Acute Abdomen

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Continuing Education Activity

Acute abdominal pain is a common emergency room complaint, with causes ranging from benign to life-threatening conditions requiring urgent intervention. The differential diagnosis is broad, including infections, inflammatory processes, vascular occlusion, aortic dissection, bowel obstruction, undiagnosed tumors, or a ruptured viscous. Patients often present with sudden abdominal pain, sometimes accompanied by fever, nausea, vomiting, or distension. A thorough history and physical examination, including vital signs and an abdominal assessment, are essential. Signs of peritonitis, shock, or obstruction necessitate urgent evaluation. Clinicians should tailor further diagnostic testing based on clinical presentation while providing appropriate analgesia.

This activity for healthcare professionals enhances the learner's understanding of evaluating and managing patients presenting with an acute abdomen. They will learn to differentiate between benign and life-threatening conditions, refine their clinical decision-making skills, and implement evidence-based strategies for imaging utilization. The activity will emphasize the importance of thorough history-taking and physical examination, appropriate use of ultrasound and computed tomography scans, and recognizing critical findings that necessitate urgent intervention. Participants will gain a deeper insight into the condition's clinical manifestations, diagnostic strategies, and therapeutic interventions. Clinicians can optimize patient care, mitigate unnecessary testing, ensure timely and appropriate specialty referrals, improve patient safety, and enhance healthcare outcomes by properly evaluating patients with an acute abdomen. Greater proficiency increases the learner's ability to collaborate within an interprofessional team caring for patients with acute abdominal pain.

Objectives:

  • Identify key signs and symptoms indicative of an acute abdomen to facilitate early diagnosis.

  • Differentiate between various causes of acute abdomen, such as surgical and nonsurgical conditions.

  • Implement evidence-based treatment protocols tailored to the underlying cause of acute abdomen.

  • Collaborate with multidisciplinary teams to ensure comprehensive patient care and follow-up care plans to monitor recovery and prevent complications.

Introduction

Acute abdominal pain is one of the most common complaints of patients presenting to the emergency room. Although the underlying cause is often benign, serious underlying pathology may also be present, and clinicians must be able to recognize patients who require urgent evaluation and intervention. The causes of an acute abdomen are diverse, making the differential diagnosis complex. Some potential causes include infections, inflammatory processes, vascular occlusion, aortic dissection, or bowel obstruction. Less apparent sources may involve undiagnosed tumors or a ruptured viscous.[1][2][3] Patients typically experience a sudden onset of abdominal pain potentially accompanied by fever, nausea, vomiting, or abdominal distension.[4]

The evaluation of acute abdominal pain begins with obtaining a detailed description of the pain, including the location, presence of radiation, timing, quality, severity, aggravating or relieving factors, and associated symptoms. All patients should have their vital signs measured and undergo a complete abdominal examination, including inspection, auscultation, percussion, and palpation, with the remaining physical examination guided by the patient's history. Patients with an acute abdomen appear acutely ill with such features as shock, peritonitis, guarding, absent bowel sounds, and rebound tenderness. Other findings may include evidence of dehydration, dysuria, vomiting, and altered bowel activity.[5][6]

Patients with unstable vital signs, signs of peritonitis, or suspected life-threatening conditions, such as acute bowel obstruction, mesenteric ischemia, perforation, or ectopic pregnancy, require urgent or surgical evaluation. In addition, patients presenting with fever, jaundice, or right upper quadrant pain should also undergo prompt assessment. A patient presenting with abdominal pain that does not appear acute should similarly undergo thorough questioning. Clinicians should determine further evaluation, including laboratory and imaging, based on symptoms. Appropriate analgesia should not be withheld during the assessment.[7]

Etiology

The acute abdomen encompasses various potential causes, ranging from gastrointestinal and genitourinary issues to vascular and infectious conditions. Clinicians must obtain a detailed history, perform a thorough physical examination, conduct imaging studies, and obtain laboratory results to identify the underlying etiology and guide appropriate management accurately.

The following list includes potential gastrointestinal causes of the acute abdomen:

  • Appendicitis;
  • Perforated peptic ulcer;
  • Acute pancreatitis;
  • Cholecystitis;
  • Diverticulitis;
  • Ruptured diverticulum;
  • Ovarian torsion;
  • Volvulus;
  • Small bowel obstruction;
  • Lacerated spleen or liver; and
  • Ischemic bowel.[1][2][3] 

Peritonitis, commonly resulting from bacterial infection, is another potential cause of an acute abdomen. This condition can arise from various conditions, including surgery, organ perforation, pelvic inflammatory disease, ascites, tuberculosis, liver disease, malignancy, trauma, feeding tubes, and peritoneal dialysis.[8][9][10] Vascular events causing an acute abdomen are mesenteric ischemia and ruptured abdominal aortic aneurysm.[11][12] Obstetric and gynecologic causes include a ruptured ectopic pregnancy, pelvic inflammatory disease, and ovarian torsion.[13] Urologic conditions, such as ureteral colic and pyelonephritis, can also present with acute abdominal pain. Newborns and infants can present with conditions such as necrotizing enterocolitis, midgut volvulus, and intussusception. The most common cause of acute abdomen in the pediatric population is acute appendicitis.[14]

Epidemiology

Abdominal pain is responsible for 7% to 10% of emergency department visits and accounts for 5 to 10 million patient encounters annually in the United States.[15] Nearly 9% of all pediatric primary care visits are due to acute abdominal pain.[4] A recent retrospective study reveals that nonspecific abdominal pain and renal colic make up nearly 60% of these diagnoses.[16] In patients older than 65, conditions such as diverticulitis and cholecystitis are more common, whereas those younger than 65 are more commonly diagnosed with renal colic and appendicitis.[15]

Acute abdomen accounts for approximately 14% of patients who present with nontraumatic abdominal pain. The incidence of acute abdomen is higher in males compared to females, with an incidence of 62.61% and 37.39%, respectively.[17] In adults, patients are most commonly affected in their mid to late twenties, with appendicitis, acute cholecystitis, and acute pancreatitis being the most common causes.[17] In the pediatric population, the most common etiology of acute abdomen varies by age. In infants, incarcerated inguinal hernia and intussusception are the most common causes, whereas acute appendicitis is the most prevalent in children older than 1.[18]

Pathophysiology

Clinicians describe abdominal pain as visceral, somatoparietal, or referred depending on the pain receptors involved.

Visceral Pain Receptors

Visceral pain receptors are located on serosal surfaces, in the mesentery, within intestinal muscle, and in the mucosa of hollow organs. Stretch is the primary stimulus involved in visceral pain perception. However, additional mechanical and chemical stimuli, such as tension, distention, contraction, traction, compression, torsion, and ischemia, stimulate these receptors. Unmyelinated C-fibers entering the spinal cord bilaterally at multiple levels transmit visceral pain, which patients commonly describe as dull, poorly localized, and felt along the midline. Visceral pain is associated with 3 anatomical pain regions. Pain from foregut structures, such as the lower esophagus and stomach, occurs in the epigastric area; midgut structures, such as the small intestine, in the periumbilical region; and hindgut structures, such as the colon, in the lower abdomen.[19]

Somatoparietal Pain Receptors 

Somatoparietal pain receptors, located in the parietal peritoneum, the muscle, and the skin, are activated by inflammation, stretching, or tearing. These pain signals are transmitted by myelinated A-δ fibers to specific dorsal root ganglia. Patients often describe somatoparietal pain as a sharp, more intense, and more localized sensation compared to visceral pain.[19] 

Referred Pain

Referred pain occurs due to the convergence of afferent neurons from different areas at a shared spinal cord level. When visceral and somatic pain signals converge, the brain cannot distinguish the visceral signals from the more common signals that arise from somatic receptors. As a result, the brain attributes the pain to the more familiar somatic regions rather than the internal organs. Common examples are pain due to cardiac ischemia felt in the neck, left shoulder, and down the left arm and cholecystitis felt in the left scapula.[19]

History and Physical

Most patients with acute abdominal pain have a self-limited etiology. The primary goal of the initial history and physical examination is to determine which patients require urgent or emergent intervention. Identifying a patient with a full-blown acute abdomen is typically less challenging compared to recognizing an incipient abdominal catastrophe in a patient presenting with early, nonspecific symptoms of abdominal pain, making a careful history and physical examination essential.

History

Key historical elements to consider include:

  • Location and radiation of the pain
  • Information regarding the onset, frequency, and duration of the pain
  • Pain severity
  • Pain description such as burning, gnawing, or stabbing 
  • Precipitating factors such as eating or moving
  • Alleviating measures such as eating or assuming a particular position 
  • Associated symptoms such as nausea, vomiting, fever, diarrhea, constipation, hematochezia, dysuria, hematuria, weight loss, anorexia, cough, chest pain, shortness of breath, or orthopnea
  • Sexual history, including risk for sexually transmitted infections, last menstrual period, dyspareunia, and dysmenorrhea
  • Past medical history, including previous surgeries, alcohol use disorder, hypertension, and cardiovascular disease, to assess for the risk of bowel obstruction due to adhesions, myocardial infarction, pancreatitis, gastritis, abdominal aortic aneurysm, and liver dysfunction
  • Medication history, including medications that may cause constipation; recent antibiotic use, which may cause Clostridioides difficile; nonsteroidal anti-inflammatory medications that increase the risk of peptic ulcer disease; and chronic corticosteroids that can cause immunosuppression
  • Alcohol consumption to assess for possible liver disease
  • Travel history for patients with a history consistent with colitis or gastroenteritis

Potential Causes of Pain Based on Location

The location of abdominal pain can provide valuable clues for clinicians in identifying the underlying cause. Pain from different parts of the abdomen often corresponds to specific organs or conditions, allowing healthcare providers to narrow down differential diagnoses.

  • Left upper quadrant pain
    • Splenomegaly
    • Splenic infarct
    • Splenic abscess
    • Splenic rupture
  • Epigastric pain
    • Myocardial infarction
    • Acute and chronic pancreatitis
    • Peptic ulcer disease
    • Gastroesophageal reflux disease
    • Gastritis
    • Gastroparesis
  • Right upper quadrant pain:
    • Biliary colic;
    • Acute cholecystitis;
    • Acute cholangitis;
    • Sphincter of Oddi dysfunction;
    • Acute hepatitis;
    • Perihepatitis;
    • Liver abscess;
    • Budd-Chiari syndrome; and
    • Portal vein thrombosis.[20][6]

Physical Examination 

The physical examination must be focused and completed promptly. Clinicians should note abnormal vital signs and the overall discomfort of the patient. A complete abdominal examination, beginning with inspection, is essential. A patient who is completely immobilized and experiences increased pain when bumped or when the bed is moved is a sign of peritonitis. Writhing in pain is often an indication of ischemia or biliary colic. Clinicians should auscultate bowel sounds before palpating the abdomen, as this may reveal absent or hypoactive bowel sounds.[21][22] Tinkling, high-pitched sounds often indicate a bowel obstruction. Percussion follows, lightly at first, to identify ascites and hepatomegaly. Patients with peritonitis experience pain with gentle percussion. Tympany signifies a distended bowel, and dullness may indicate a mass. Shifting dullness indicates ascites.[23] Palpation with the examining hand can reveal rebound tenderness and guarding suggestive of peritonitis. Clinicians should note the location of the positive palpatory findings to provide clues to the underlying cause.  

Classic teaching demands a rectal examination for every patient with abdominal pain. Literature suggests that a rectal examination, at least in appendicitis, adds no helpful information. Indeed, a rectal examination is essential when gastrointestinal bleeding or prostate issues are suspected. A pelvic examination is necessary in females with lower abdominal pain or when clinicians suspect pelvic pathology. A young male with lower abdominal pain needs a testicular examination to exclude testicular torsion. Examination for hernias should be routine.

Clinicians should examine the eyes and skin for jaundice. Patients with cardiac or respiratory symptoms must undergo a cardiovascular and respiratory examination. Evidence of extraintestinal manifestations can indicate the presence of inflammatory bowel disease. 

Classic Presentation of Abdominal Pain

Although some causes of abdominal pain have classic presentations, many conditions do not present typically. Therefore, clinicians must maintain a high index of suspicion, regardless of the presentation. The following examples are some of the common presentations of acute abdominal pain that require urgent or emergent intervention. 

Abdominal aortic aneurysm: Most patients with an abdominal aortic aneurysm are asymptomatic. If symptomatic, an unruptured abdominal aortic aneurysm typically presents with abdominal, back, or flank pain. The classic presentation of a ruptured abdominal aortic aneurysm is severe pain, hypotension, and a pulsatile abdominal mass. 

Abdominal obstruction: Clinicians should suspect an intestinal obstruction when a patient presents with pain, vomiting, and obstipation. Classic examination findings include abdominal distension, high-pitched or absent bowel sounds, tenderness, and a tympanic abdomen.

Acute appendicitis: The pain of appendicitis typically begins in the periumbilical region and migrates to the right lower quadrant over McBurney's point. Associated symptoms are anorexia, nausea, low-grade fever, and vomiting. 

Acute cholecystitis: This condition typically presents with severe, persistent right upper quadrant or epigastric pain lasting more than 4 to 6 hours, accompanied by fever, abdominal guarding, a positive Murphy's sign, and an elevated white blood cell count.

Acute cholangitis: Acute cholangitis occurs when a stone occludes the biliary or hepatic ducts and presents with vague right upper quadrant pain, fever, and jaundice, known as Charcot's triad. The obstruction results in dilation and bacterial superinfection of the duct.[24]

Acute diverticulitis: Left lower quadrant pain is the most common presenting complaint of acute diverticulitis, although right lower quadrant diverticulitis is also possible. Additional possible associated symptoms are localized guarding, rigidity, and rebound tenderness. A rectal examination may reveal occult blood on stool testing or a mass or tenderness if a distal sigmoid abscess is present.[25]

Acute pancreatitis: Acute pancreatitis manifests as severe persistent left upper quadrant (LUQ) and epigastric pain radiating to the back. Nausea and vomiting are also commonly associated symptoms.

Descending aortic dissection: Aortic dissection can present with chest, back, and abdominal pain. Descending aortic dissections are more likely to cause abdominal pain. Patients may describe the pain as sharp, ripping, or tearing. Additional associated symptoms are hypotension, although hypertension is more commonly associated with descending aortic dissections and pulse deficits. Syncope, focal neurological deficits, and acute aortic regurgitation are more commonly associated with ascending aortic dissections.[26][27] 

Ectopic pregnancy: First-trimester vaginal bleeding and abdominal pain 6 to 8 weeks after the last menstrual period are the classic presenting features of an ectopic pregnancy. 

Incarcerated hernia: Incarcerated hernias may be painful to palpation. The overlying skin may be erythematous, and the patient may be febrile. Patients generally do not have peritonitis as the necrotic bowel remains in the incarcerated sac. However, if the incarcerated hernia is reduced, peritoneal signs may develop.[28] 

Intestinal malrotation with volvulus: Children with intestinal malrotation and volvulus present with abdominal pain, often out of proportion to examination findings, bilious vomiting, peritonitis, hematochezia, abdominal distension, and hemodynamic instability. A cecal or sigmoid volvulus in adults generally presents with a gradual onset of abdominal pain, nausea, bloating, and constipation or constipation but can present with severe acute abdominal pain. Vomiting typically begins a few days after the pain starts. The pain linked to a cecal or sigmoid volvulus is generally persistent and intense, with intermittent colicky episodes occurring during peristalsis.[29] 

Intussusception: An infant or toddler with an intussusception classically presents with sudden, severe, and progressively worsening abdominal pain. The pain presents as intermittent episodes of inconsolable crying and pulling the legs up toward the abdomen. The episodes generally occur every 15 to 20 min and increase in frequency and intensity. Vomiting is also a common symptom. Initially, the vomit may be nonbilious but often turns bilious as the condition advances. Occasionally, the clinician may palpate a sausage-shaped mass in the right abdomen. Approximately 25% of affected children have bloody stools, but stool guiac is often positive. Rarely do the stools appear like the classic currant jelly often described, as this is a late finding due to significant bleeding and sloughing of the mucosa. 

Mesenteric ischemia: Mesenteric ischemia presents as acute, severe, and diffuse abdominal pain. The pain is often disproportionate to what the clinician finds on examination. Acute colonic ischemia is generally on the left side and associated with hematochezia and tenesmus. At the same time, an arterial embolism to the proximal superior mesenteric artery presents with pain in the periumbilical area. Please see StatPearls' companion reference, "Acute Mesenteric Ischemia," for more information.

Necrotizing enterocolitis: The most common sign of necrotizing enterocolitis is a sudden change in feeding tolerance.[39] Additional findings may include abdominal wall erythema, crepitus, and induration. Infants may also experience apnea, temperature instability, and lethargy. Hypotension and septic shock occur in severe cases. 

Ovarian torsion: Ovarian torsion manifests as severe pelvic pain, nausea, and vomiting in a patient with an adnexal mass. 

Perforation of the gastrointestinal tract: Patients with perforation may present with chest, neck, or abdominal pain. The sudden onset of worsening pain after medical instrumentation should alert the clinician to the possibility of perforation. Associated symptoms depend on the organ affected and the contents released. Patients can develop peritonitis, a fistula, or an abscess if the fluid remains contained.

Splenic rupture: Splenic rupture is typically due to trauma. Patients may complain of left upper abdominal, left chest wall, or left shoulder pain. Pain referred to the left shoulder that worsens with inspiration is called Kehr's sign and is due to blood adjacent to the left hemidiaphragm irritating the phrenic nerve.

Testicular torsion: Testicular torsion typically presents in children and adolescents with severe testicular and lower abdominal pain. Commonly associated symptoms are nausea and vomiting.

Evaluation

The history and physical examination guide the diagnostic evaluation of acute abdominal pain. Patients with unstable vital signs, evidence of peritonitis, or suspected life-threatening conditions such as ectopic pregnancy, myocardial infarction, bowel obstruction, abdominal aortic aneurysm, acute mesenteric ischemia, or perforation warrant urgent evaluation in the emergency department. Patients with potential life-threatening abdominal pathology should undergo simultaneous evaluation and resuscitation. Healthcare professionals initially assess the patient's general appearance, airway, breathing, and vital signs. A bedside fingerstick glucose can assess for possible diabetic ketoacidosis, an electrocardiogram assesses for cardiac and electrolyte abnormalities, and a bedside ultrasound is a quick tool used to assess for abdominal aortic aneurysm, hydronephrosis, pericardial effusion, and hemoperitoneum.

If the suspected etiology is perforation of an abdominal organ or sepsis due to an abdominal origin, an upright portable chest radiograph is the initial imaging test of choice. If the bedside ultrasound and upright chest radiograph do not provide adequate diagnostic clues, computed tomography (CT) of the abdomen and pelvis with intravenous (IV) contrast is the next step. An abdominal and pelvic ultrasound is the initial imaging modality in pregnant patients evaluating for an intrauterine pregnancy, appendicitis, nephrolithiasis, cholecystitis, cholelithiasis, and uterine rupture. If the ultrasound is not helpful and additional imaging is necessary, abdominal magnetic resonance imaging (MRI) is the next step. 

For less emergent cases, the location of the pain helps guide evaluation, much like it does when developing the differential diagnosis. When examining children, it is essential to consider the child's age and the likely diagnosis.

Right Upper Quadrant Pain

Right upper quadrant pain is associated with the liver or biliary tree. However, as the liver only becomes painful when its capsule is stretched, the primary causes are related to the biliary tree. Patients with right upper quadrant pain should undergo a thorough workup, including a complete blood count (CBC), serum electrolyte, aminotransferases, alkaline phosphatase, serum bilirubin, lipase, and amylase. In addition, an abdominal ultrasound is the imaging modality of choice.[30][31][32]

Epigastric Pain

The initial evaluation of epigastric pain is the same as that of right upper quadrant pain. Patients with cardiac risk factors and symptoms suggestive of a cardiac issue—such as dyspnea, exertional symptoms, diaphoresis, nausea, or vomiting—should undergo an electrocardiogram, troponin testing, and a chest radiograph. Based on the results, further evaluations may include echocardiography, stress testing, coronary CT angiography, and angiography. Endoscopy may be indicated for patients with suspected peptic ulcer disease.

Left Upper Quadrant Pain

LUQ pain may be due to underlying splenic or epigastric causes. Patients with splenic pathology likely experience early satiety, abdominal fullness or distension, or pain referred to the chest or left shoulder. Ultrasound is the preferred imaging tool for determining the size of the spleen. A CBC can evaluate for hematologic disorders, whereas serum transaminases assess potential liver involvement. Additional laboratory tests include HIV testing if indicated, blood cultures for suspected infection, and a glucocerebrosidase assay to exclude Gaucher disease. CT or MRI may be necessary for focal lesions such as infarctions or abscesses. Chest radiograph may reveal a pleural effusion associated with a splenic abscess.[33] Additional testing depends on the initial evaluation results, with patients with suspected malignancy requiring bone marrow or lymph node biopsy.

Lower Abdominal Pain

Lower abdominal pain can arise from the distal colon, pelvis, and testicles. Clinicians must exclude pregnancy in all patients with childbearing potential. Potential pelvic sources of the acute abdomen include pelvic inflammatory disease, ectopic pregnancy, tubo-ovarian abscess, and ovarian torsion. In addition, clinicians must consider urinary tract obstruction and infection, appendicitis, incarcerated hernia, and diverticulitis. Laboratory testing and imaging depend on the history and physical examination. Suggested diagnostic testing includes the following:

  • CBC for patients with bleeding or signs of infection 
  • Type and cross-match for individuals with significant hemorrhage
  • Urinalysis and possibly urine culture for suspected urinary tract infection or acute complicated urinary tract infection
  • Blood cultures for suspected disseminated infection
  • Testing for gonorrhea, chlamydia, trichomoniasis, and bacterial vaginosis in patients with risk factors or symptoms of pelvic inflammatory disease
  • Transvaginal and transabdominal ultrasound to assess for free fluid indicating a ruptured ectopic pregnancy, ruptured ovarian cyst, or trauma and locating a pregnancy in patients with a positive pregnancy test
  • CT of the abdomen and pelvis in nonpregnant adults with suspected appendicitis, diverticulitis, small bowel obstruction, or nephrolithiasis or when the ultrasound findings are unrevealing
  • Colonoscopy for patients with anemia and abdominal pain to evaluate for colon cancer or subacute abdominal pain and diarrhea to assess for inflammatory bowel disease
  • Scrotal ultrasound for abnormal scrotal examination

Diffuse Abdominal Pain

Diffuse abdominal pain can be more challenging to diagnose and result from pulmonary, cardiac, or intraabdominal pathologies. The initial evaluation for diffuse abdominal pain includes:

  • CBC with differential
  • Serum electrolytes
  • Amylase and lipase
  • Calculation of the anion gap
  • Blood urea nitrogen and creatinine
  • Serum glucose
  • Aminotransferases, alkaline phosphatase, and bilirubin
  • Calcium
  • Pregnancy test in all patients with childbearing potential

The remaining evaluation depends on the results of the initial assessment. Some additional considerations are as follows:

  • Chest radiograph for patients with diffuse upper abdominal pain and suspected pneumonia
  • Abdominal radiographs to evaluate for pneumoperitoneum and bowel obstruction
  • CT pulmonary angiogram for patients with diffuse upper abdominal pain and suspected pulmonary embolism
  • CT scan of the abdomen and pelvis for patients with a suspected volvulus, bowel obstruction, and  hemodynamically stable patients with a suspected abdominal aortic aneurysm
  • Abdominal ultrasound for patients with a suspected ruptured abdominal aortic aneurysm who are hemodynamically unstable 
  • IV-enhanced CT angiogram of the chest, abdomen, and pelvis for patients with concern for mesenteric ischemia and aortic dissection

The American College of Radiology (ACR) Appropriateness Criteria are evidence-based guidelines that help healthcare professionals determine the best imaging or treatment for a patient. Clinicians can access the criteria at the American College of Radiology's website: https://www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Appropriateness-Criteria.

Children

The evaluation of abdominal pain in children follows a similar approach to adults but requires specific considerations. Clinicians must exclude malrotation, a surgical emergency, in a child younger than 1 who presents with bilious vomiting. Children with abdominal pain and pharyngitis should undergo rapid strep testing. Healthcare professionals infrequently use CT scans of the abdomen in children due to the risks associated with radiation exposure. For children presenting with bilious vomiting, severe abdominal pain, abdominal distension, or signs of peritonitis, an abdominal radiograph is usually the initial diagnostic step. This imaging modality swiftly detects perforation through the presence of free air and identifies bowel obstruction by revealing air-fluid levels and distended bowel loops.

Ultrasound effectively visualizes intussusception, whereas a contrast enema can diagnose and treat intussusception. An upper gastrointestinal contrast series remains the imaging study of choice for malrotation with volvulus. Children who present with classic signs of appendicitis should undergo evaluation by a pediatric surgeon before undergoing imaging. If the presentation is atypical or the examination findings are unclear, imaging with abdominal ultrasound is preferred. 

Children with suspected necrotizing enterocolitis should undergo abdominal radiographs, which reveal pneumatosis intestinalis. Some centers use ultrasonography, which shows free air, focal fluid collections, increased bowel wall thickness, and echogenicity.[34] Infants with necrotizing enterocolitis also warrant a sepsis evaluation, CBC, serum electrolytes, BUN, creatinine, and glucose levels. Persistent hyponatremia, hyperglycemia, and metabolic acidosis all indicate necrotic bowel and sepsis.[35] Clinicians can follow serum lactate levels to monitor disease progression and improvement.

Treatment / Management

Clinicians initiate resuscitation alongside the initial evaluation, not delaying specialty consultation while awaiting imaging results.[34] They promptly attach patients to a cardiac monitor and treat those with peritonitis, hypotension, or a toxic appearance by establishing large-bore IV access, administering crystalloid fluids, and using vasopressors for septic shock. Patients with adrenal insufficiency or chronic glucocorticoid use receive stress-dose steroids, and patients with evidence of hypovolemia and hemorrhage receive blood products. Broad-spectrum antibiotics targeting gram-negative and anaerobic enteric organisms are necessary when infection, peritoneal contamination, or sepsis is suspected.

Healthcare professionals should remember that adequate pain management is essential and does not alter the assessment.[35] Potential interventions include acetaminophen, parenteral ketorolac, and opioids. Clinicians must exercise caution with ketorolac, as it can exacerbate gastritis, peptic ulcer disease, and acute kidney injury. The diagnosis dictates further intervention and specialty consultation. Typical specialty involvement includes general or vascular surgery, gynecology, interventional radiology, urology, and gastroenterology. Patients with suspected perforation and pneumoperitoneum on initial radiographs warrant immediate surgical referral. In addition, ruptured ectopic pregnancies, testicular torsion, ovarian torsion, an obstructing infected kidney stone, and a ruptured abdominal aortic aneurysm are some examples of conditions that warrant immediate specialty and surgical referral.

Differential Diagnosis

Although the majority of patients presenting with acute abdominal pain have a benign underlying cause, the differential diagnosis is extensive, and clinicians must rely on an organized approach to determine which patients require immediate surgical intervention or medical therapy. The following list includes potential differential diagnoses for patients presenting with acute abdominal pain: 

  • Abdominal aortic aneurysm;
  • Abdominal compartment syndrome;
  • Abdominal migraine;
  • Acute hepatic porphyrias;
  • Acute appendicitis;
  • Acute cholangitis;
  • Acute cholecystitis;
  • Acute diverticulitis;
  • Acute hepatitis;
  • Acute intestinal ischemia;
  • Acute pancreatitis;
  • Acute peptic ulcer;
  • Acute peritonitis;
  • Acute pyelonephritis;
  • Acute ureteral colic;
  • Adrenal crisis;
  • Angioedema;
  • Biliary colic;
  • Bowel obstruction;
  • Bowel volvulus;
  • Budd-Chiari syndrome;
  • Carcinoid;
  • Celiac artery compression syndrome;
  • Celiac disease;
  • Colonic pseudo-obstruction;
  • Ectopic pregnancy with a tubal rupture;
  • Eosinophilic gastroenteritis;
  • Epiploic appendagitis;
  • Familial Mediterranean fever;
  • Gastroparesis;
  • Helminthic infections;
  • Herpes zoster;
  • Hemoperitoneum;
  • Hypercalcemia;
  • Hypothyroidism;
  • IgA vasculitis;
  • Incarcerated hernia;
  • Intussusception;
  • Ketoacidosis;
  • Kidney stone;
  • Lactose intolerance;
  • Lead poisoning;
  • Liver abscess;
  • Malignancy;
  • Meckel's diverticulum;
  • Mesenteric ischemia;
  • Narcotic bowel syndrome;
  • Necrotizing enterocolitis;
  • Ovarian torsion;
  • Paroxysmal nocturnal hemoglobinuria;
  • Pelvic inflammatory disease;
  • Perihepatitis;
  • Portal vein thrombosis;
  • Pseudoappendicitis;
  • Pulmonary etiologies such as pneumonia;
  • Rectus sheath hematoma;
  • Renal infarction;
  • Rib pain;
  • Ruptured spleen;
  • Sclerosing mesenteritis;
  • Sickle cell anemia;
  • Sphincter of Oddi dysfunction;
  • Splenic abscess;
  • Splenic infarct;
  • Splenic rupture;
  • Streptococcal pharyngitis;
  • Thoracic duct-venous junction obstruction;
  • Tubo-ovarian abscess; and
  • Wandering spleen.[6][36][37][38]

Prognosis

The overall prognosis for a patient with an acute abdomen depends on both the underlying cause and the timeliness of treatment.[39][40] Despite advanced diagnostic tools, undifferentiated abdominal pain remains the diagnosis for approximately 25% of patients discharged from the emergency department and between 35% and 41% of those admitted to the hospital.[2][6][7][8] Approximately 80% of patients discharged with undifferentiated abdominal pain improve or become pain-free within 2 weeks of presentation.

Complications

If left untreated, an acute abdomen may result in the following:

  • Sepsis
  • Necrosis or gangrene of the bowel
  • Fistula
  • Death
  • Secondary wound complications
  • Acute kidney injury

Postoperative and Rehabilitation Care

Most patients with an acute abdomen require treatment in an intensive care unit setting. IV hydration, nasogastric decompression, and pain control are often required. The use of antibiotics depends on the specific diagnosis. Close monitoring is essential, as patients may develop complications such as atelectasis, ileus, wound infections, deep vein thrombosis, and pneumonia.

Consultations

When treating a patient with an acute abdomen, timely and appropriate consultations with specialists are critical to ensure accurate diagnosis and effective treatment. Clinicians should not postpone specialty consultations while awaiting imaging results. Clinicians in the following specialties may be necessary depending on the underlying cause:

  • Infectious disease 
  • Obstetrics and Gynecology
  • Urology
  • Vascular surgery
  • General surgery
  • Radiology and interventional radiology
  • Cardiology
  • Gastroenterology
  • Pulmonology
  • Thoracic surgery

Deterrence and Patient Education

Though most episodes of acute abdominal pain have a benign, self-limited etiology, some have an underlying serious cause. Because the differential diagnoses for abdominal pain are extensive, providing information regarding the symptoms of potentially life-threatening causes will help guide patients on when to seek immediate medical care. Patients should understand that the sudden onset of severe abdominal pain is a sign of a potentially serious underlying condition. Additional symptoms that should raise concern are nausea, vomiting, fever, blood in the stool or vomit, dark, tarry stools, or pain that worsens when someone bumps them or if they hit a bump in the road while riding in the car. Symptoms unique to children may be inconsolable crying or intermittent colicky pain. 

Patients can lower their risk of acute abdomen by adopting a healthy lifestyle, consuming a well-balanced diet, and limiting alcohol and tobacco use. Additionally, regularly monitoring chronic conditions such as gallstones and inflammatory bowel disease, along with following recommended screening guidelines for colon cancer and abdominal aortic aneurysms, can help prevent its occurrence. Clinicians should educate patients taking high-risk medications, such as nonsteroidal anti-inflammatory drugs, on the signs of adverse effects like peptic ulcer disease and when to seek medical care. Healthcare professionals must educate patients on the importance of following postoperative instructions. Proper patient education can prevent postoperative complications like wound infections, deep vein thrombosis, and pulmonary embolism. 

Enhancing Healthcare Team Outcomes

Severe, often rapid onset abdominal pain that necessitates prompt evaluation and management characterizes an acute abdomen. Clinically, it may manifest as localized or diffuse pain, peritoneal signs such as guarding and rebound tenderness, hemodynamic instability, and associated symptoms, including nausea, vomiting, fever, or altered bowel habits. A comprehensive history and physical examination, focusing on pain characteristics and risk factors, guide the initial diagnostic and management approach. Laboratory tests and imaging studies aid in diagnosis, with the ACR Appropriateness Criteria as a valuable tool in selecting the most effective imaging modality. These criteria enhance care quality, optimize radiology use, minimize unnecessary radiation exposure, and prevent diagnostic delays.

Management varies based on the underlying etiology, ranging from supportive care and antibiotics for infections to urgent surgical intervention for conditions such as perforation, ischemia, or obstruction. Early consultation with surgeons and other specialists and serial reassessments are crucial to preventing complications.

While surgeons often play a central role, an interdisciplinary healthcare team is essential for optimal patient outcomes. Nurses contribute by monitoring vital signs, pain levels, and postoperative recovery, including bowel function and wound healing. Pharmacists ensure appropriate analgesic, antiemetic, and antibiotic selection and dosing. Radiologists are instrumental in diagnosing underlying causes and providing interventional therapies when needed, while physical therapists facilitate early ambulation and functional recovery.

Effective interprofessional communication is vital for seamless collaboration and coordinated care. Healthcare professionals must exchange relevant patient information, discuss treatment plans, and address concerns promptly to ensure timely and appropriate management. By integrating their expertise, fostering teamwork, and emphasizing clear communication, physicians, advanced practitioners, nurses, pharmacists, and other healthcare professionals can enhance patient-centered care, improve outcomes, and optimize team performance in managing acute abdominal conditions.


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