Subphrenic abscesses represent infected collections bounded above by the diaphragm, and below by the transverse colon and mesocolon, and the omentum. Described by Barlow in 1845, Von Volkman recorded the first surgical cure in 1879 through abdominal and thoracoscopic exploration.
Usually, subdiaphragmatic abscesses arise from abdominal surgery, trauma, or local inflammation in the space between the liver, intestines, and lungs, making drainage a challenge. The diagnosis of subphrenic abscess can be difficult, and hence it is known by the famous aphorism: 'pus somewhere, pus nowhere else, pus under the diaphragm.'
The formation of the subphrenic abscess occurs after bowel content, and gut bacteria contaminate the peritoneal cavity. A retrospective review of 52 patients between 1974 and 1988 showed most infections to be polymicrobial, with predominantly aerobic isolates with Escherichia coli, Enterococcus spp, Enterobacter, and Staphylococcus aureus. The most common anaerobes are Peptostreptococcus, Bacteroides fragilis, Clostridium spp, and Prevotella.
Staphylococcus aureus is the most common isolate after gastric surgery, and Bacteroides fragilis and Clostridium spp are the most common after colon surgery and/or appendicitis. Enterococcus group D predominates after biliary surgery, and Fusobacterium and Prevotella species are the cause following gastric or duodenal surgery. Risk factors include previous abdominal surgery that involved significant contamination from the gastrointestinal tract such as perforated appendicitis, gastric ulcer, or diverticulitis, gastric and intestinal perforation, mesenteric ischemia, appendicitis, trauma, empyema, and sepsis.
Recent advances in early diagnosis and non-operative management of subphrenic abscess have decreased the incidence and improved the outcomes. A primary subphrenic abscess is defined as an abscess that developed in the intraabdominal space without the introduction of bacteria from the outside of that space. The actual frequency of primary subphrenic abscess is not known and is thought to be very rare. It constituted 13% in one case series.
Most subphrenic abscesses are caused by the introduction of bacteria into the subphrenic space. Among secondary subphrenic abscesses, gastric and biliary tree surgery constitutes 52% of abscesses. Appendicitis contributes to 8%, while colonic surgery and trauma comprise 19% and 8%, respectively. Left-sided abscesses occur in 40%, and multiple space abscesses in 20% of patients.
The diaphragm, an intrathoracic organ, separates the thoracic and abdominal cavities and is covered by pleura and peritoneum, as it is both extrapleural and extraperitoneal. The subphrenic space is divided by the falciform ligament.
The clinical presentation varies with the anatomic location of the subphrenic abscess. However, fever, upper quadrant pain, costal margin tenderness, shoulder pain, abdominal tenderness, and dyspnea may be present. It may also present as a hiccup, cough, or unexplained pulmonary manifestations like pneumonia, pleural effusion, and basal atelectasis. Pyrexia of unknown origin is not uncommon. The majority of the patients who are not treated immediately will progress to have a systemic inflammatory response syndrome and develop tachycardia, hypotension, and low urine output, eventually leading to multiorgan failure and death.
Leukocytosis with neutrophilia and an elevated sedimentation rate are common. A chest x-ray may show elevation of the hemidiaphragm, pleural effusion, and lung abnormalities. Blood cultures indicating polymicrobial bacteria are highly suggestive of a subphrenic abscess. Abdominal ultrasound is the gold standard for right-sided subphrenic abscess, with high sensitivity for fluid collections. Computerized tomography (CT) scan seems better for the detection of a left-sided subphrenic abscess. CT scan is considered the diagnostic imaging of choice in any patient with suspected intraabdominal abscess.
Sagittal imaging on CT scan is best for visualizing subdiaphragmatic abscesses. Abdominal magnetic resonance imaging (MRI) and an indium-111-labeled leukocyte scan may be helpful for hidden intraabdominal or subphrenic abscesses. MR enterography is the investigation of choice in patients with inflammatory bowel disease. Blood gas analysis may reveal respiratory alkalosis initially due to hyperventilation and may progress to metabolic acidosis if left untreated.
Management of subphrenic abscess includes antibiotics, drainage of the abscess, and general care of the patient.
Broad-spectrum parenteral antibiotics should be initiated empirically at the time of diagnosis, which should cover both aerobes and anaerobes. Later, the antibiotics can be modified as per culture and sensitivity. Early initiation of antibiotics improves outcomes. Combination therapy or a single broad-spectrum antibiotic can be initiated. Cephalosporins with metronidazole can be considered as the initial choice. In immunosuppressed patients, antifungals covering candida may be indicated. The antifungal of choice depends on the patient's general condition. Azoles are preferred if the patient is stable and if cultures show sensitivity to azoles. In critically ill patients and non-albicans candida, echinocandins like anidulafungin are the drug of choice.
The duration of antibiotics depends on the etiology and extent of the source control. The Surgical Infection Society guidelines suggest 96 hours for well-controlled intrabdominal sepsis and 5-7 days for those in whom definitive source control procedure is not performed. Cultures should be obtained, and antibiotics should be tailored based on speciation and sensitivity of those cultures.
As with most abscesses and contained infected spaces, drainage is the definitive treatment of a subdiaphragmatic abscess. It prevents progressive sepsis. It can be accomplished either by percutaneous or surgical drainage. Percutaneous drainage is least invasive and just as effective as surgical drainage and is currently the standard of care. CT guided drainage with interventional radiology is highly effective and can prevent the morbidity and mortality associated with surgical drainage.
Percutaneous computed tomography (CT)-guided drainage is considered the gold standard in management and has a very high success rate. The advantages include that it avoids general anesthesia, especially in the elderly with multiple comorbidities, prevents complications of the surgical wound, and reduces the length of hospitalization. Percutaneous drainage can be used as both diagnostic and therapeutic modality. Especially in critically ill patients, it can be used to control sepsis and improve the general condition of the patient before definitive surgical treatment. Persistent drainage usually suggests the presence of an enteric fistula, which can be diagnosed with a contrast CT. Complications include bleeding, injury to nearby visceral organs, pleural effusion, pneumothorax, and mediastinitis. Hence, transmural drainage has been developed using endoscopic ultrasound (EUS-TD). It has been shown to be beneficial due to real-time visualization of the abscess cavity, the use of doppler to avoid major vessels, and high success rate. Trans-esophageal and trans-gastric approaches have been tried to drain the subphrenic abscess.
If percutaneous or endoscopic drainage fails, then surgical drainage either by an open or laparoscopic method is indicated. Laparoscopic drainage is minimally invasive and permits exploration of the abdominal cavity without the use of wide incision, and hence purulent exudate can be aspirated under direct vision. If the patient does not improve with the laparoscopic technique, then an open surgical technique should be considered. The open approach may be difficult due to adhered bowel, loss of anatomic delineation, and fragile viscera. Of late, there has been increased use of open abdomen therapy (OAT), mainly in the management of abdominal compartment syndrome and trauma patients. The concept of damage control surgery is being used. The use of a vacuum dressing to close the abdomen is preferred.
The majority of the patients with a timely intervention will recover with supportive care like intravenous hydration. Patients who worsen and develop septic shock will need admission to the intensive care unit. Need for multiorgan support like mechanical ventilation, vasopressors, and dialysis will be needed in patients with significant organ failures.
In patients with gastric cancer that undergo gastrectomies, the complication of a subphrenic abscess can be as high as 4.0%. This usually happens after total gastrectomies and is thought to be caused secondary to leaks in the anastomoses. The treatment is the same for such abscesses as described above, which should include intraabdominal catheter drainage and intravenous antibiotics.
The use of computed tomography (CT) in diagnosis and drainage has led to a drastic reduction in morbidity and mortality. Multiorgan failure is the main cause of death. Early resuscitation and adequate source control have decreased the mortality due to severe sepsis from 40% to 60% to 18% to 30%.
A subdiaphragmatic abscess can cause chest complications like pleurisy, pleural effusion, empyema, lung abscess, and bronchial fistula. It can also lead to intraabdominal complications like generalized peritonitis, pelvic abscess, and abscess in the right paracolic gutter. Additionally, it can lead to systemic complications like sepsis, septic shock, and multiorgan failure.
The majority of the patients improve without any further major complications. Respiratory rehabilitation in the form of deep breathing exercises and early mobilization are important for early recovery. Adequate analgesia management with a multimodal approach is the key.
An interprofessional team comprised of an emergency clinician, radiologist, surgeon, intensivist, microbiologist, and infectious disease specialist may be needed for the management of patients with subphrenic abscess.
Subdiaphgramatic abscesses can happen as a consequence of another condition such as cholecystitis, diverticulitis, or appendicitis. Risk factors include recent surgery, diabetes, and/or inflammatory bowel disease. Patients with these risk factors should be educated to monitor for symptoms of a subphrenic abscess, including fever, pain in the abdomen, chest or shoulder pain, and anorexia. Patient outcomes depend on the cause of the infection and how quickly treatment is sought, so patients should be instructed to seek care immediately if these symptoms develop, especially after recent intraabdominal surgery.
A subdiaphragmatic abscess frequently poses a diagnostic dilemma. These patients may exhibit non-specific signs and symptoms such as abdominal pain, vomiting, nausea, and leukocytosis. While the physical exam may reveal that the patient has abdominal tenderness, it is difficult to know without proper imaging studies. While the general surgeon is almost always involved in the care of such patients, it is important to consult with an interprofessional team of specialists that include a radiologist, intensivist, microbiologist, and infectious disease specialist. The nurses are also a vital member of the interprofessional group as they will monitor the patient's vital signs and assist with the education of the patient and family. In the postoperative period, the pharmacist will ensure that the patient is on the right analgesics, antiemetics, and appropriate antibiotics. Without providing a proper history, the radiologist may not be sure what to look for or what additional radiologic exams may be needed, so good communication within the team is paramount. To improve outcomes, prompt consultation with an interprofessional group of specialists is recommended.
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