Parahiatal Hernia

Etiology

PHH is not well-described in the literature. However, like other diaphragmatic hernias, PHH can be congenital or acquired. The 2 most common congenital diaphragmatic defects are the Bochdalek hernia, a posterolateral defect arising from failure of the pleuroperitoneal folds and persistent pneumoenteric recess, and Morgagni hernia, an anteromedial defect that forms due to the failure of the septum transversum to fuse with the pleuroperitoneal membranes, esophageal dorsal mesentery, and body wall to form the diaphragm. Both conditions mostly occur on the left side of the body. Acquired defects are secondary to trauma, postesophageal surgery, or progressive diaphragmatic muscular weakness.[3][4][5] Based on established embryological evidence in the literature regarding diaphragmatic hernias, congenital PHH is a posteromedial defect arising from failure of the dorsal mesentery to develop within the diaphragm.

Epidemiology

Most PHH cases are found incidentally and presented in the literature as case reports. Therefore, the exact incidence of PHH is difficult to obtain. The incidence of PHH is estimated to be between 0.2% and 0.35%.[6] The condition is more commonly noted in older people but has no gender prevalence.[7][8]

Pathophysiology

Besides congenital weakness, acquired PHH can also occur de novo in the absence of any trauma or surgery due to progressive muscle weakness with age. Further contributing factors include a high body mass index, persistently increased intraabdominal pressure, and smoking.[9]

History and Physical

PHH may mimic the clinical presentation of other diaphragmatic hernias. Distinguishing PHHs from the more common paraesophageal hernias can thus be challenging. Patients do not share symptoms of gastroesophageal reflux disease unless a hiatal hernia coexists. Identifying these defects separately is crucial due to their implications on the choice of repair and overall patient outcomes. These defects are incidental findings in other workups or during hiatal hernia repair. The literature features case reports of urgent presentation with either intestinal incarceration or volvulus. PHH may be signified by the symptoms of epigastric discomfort, nausea, vomiting, postprandial chest pain that mimics angina, early satiety, and, in worst cases, respiratory symptoms. The patient can be anemic due to gastric erosions at the neck of the hernia, with mild discomfort in the epigastric region and reduced air entry over the left lower chest.[10]

Evaluation

Chest radiography can help evaluate large PHH defects. Depending on the contents, the air-fluid level is pathognomonic for diaphragmatic hernia, and gaseous small or large bowel loops may be noticed. Esophagogastroscopy on J-maneuver shows 2 openings: the normal esophageal hiatus where the scope passes through and, laterally, the PHH opening, with an intervening band of tissue that differentiates it from its contemporary hiatal hernia (see Image. Right Crus of Diaphragm, Sagittal View). Sometimes, PHH can be diagnosed as a gastric diverticulum because of a similar endoscopic appearance. A contrast swallow study should give evidence of other concurrent esophageal disorders, such as achalasia or gastroesophageal reflux disease, and confirm the presence of a diaphragmatic hernia. However, these findings are not diagnostic of PHH. Manometry and pH studies are recommended for inclusion in the routine workup for reflux disease to have an objective assessment through esophageal manometry and the De Meester score, respectively. These studies quantify the symptoms, informing the choice of surgical repair. A decision must be made based on the patient’s history and operative findings during surgical emergencies.[11] A computed tomography scan of the chest and upper abdomen with 3-dimensional reconstruction views is the preferred choice of investigation because it can accurately show the diaphragmatic hernia’s anatomy. The left part of the right crus is typically lateral to the esophagus. PHH lies lateral to this part of the right crus as its border. Identifying this band of tissue is the key to diagnosis (see Image. Left Crus of Diaphragm, Coronal View).[12] 

Treatment / Management

Depending on the presentation, PHH may be managed conservatively or surgically. These approaches and their indications are explained below.

Conservative Management of PHH

PHH may be dormant but later present as an emergency due to complications such as gastric volvulus. Published evidence does not support conservative management in the presence of complications.

Surgical Management of PHH

The laparoscopic approach is recommended for all large and symptomatic cases. The repair ultimately aims to reduce the hernia content and excise the sac.[13] Once the boundaries of the parahiatal defect are identified, which could only be achieved if the esophageal hiatus is thoroughly dissected, the left part of the right and left crura is approximated tension-free with interrupted nonabsorbable stitches (see Video. Repair of Parahiatal Hernia). Reinforcement techniques should be considered if the tissue quality is poor or the defect is large enough. If using a mesh, the preferred type is an absorbable biomesh. An antireflux procedure may be necessary in the presence of reflux symptoms or when the whole GEJ is disentangled.[14] The recurrence rates of gastroesophageal reflux disease, hernia, and reoperation increase when fundoplication is not performed during PHH repair. However, the risk of dysphagia is lower in such cases, though none of these differences are statistically significant. While PHH repair with fundoplication is generally recommended, forgoing the procedure may be acceptable in certain situations.[15] Partial Toupet fundoplication is the preferred and standard practice, but it depends on the surgeon’s preference and expertise (see Video. Parahiatal Hernia Repair Augmented with Mesh).(A1)

Recently, the European Association of Endoscopic Surgery made evidence-based recommendations for PHH. This guideline is intended for adult patients with moderate-to-large paraesophageal defects, types II to IV, with at least 50% of the stomach herniated into the thoracic cavity. A strong recommendation indicates that the proposed action is suitable for most patients. In contrast, a conditional recommendation suggests that most patients would choose the proposed action, necessitating joint decision-making between the surgeon and the patient. The panel recommends surgery over conservative management for asymptomatic or minimally symptomatic paraesophageal hernias, though this recommendation is conditional. However, the panel strongly recommends conservative management over surgery for frail patients with asymptomatic or minimally symptomatic paraesophageal hernias. Additionally, the panel suggests using mesh rather than sutures for hiatal closure during paraesophageal hernia repair, opting for fundoplication over gastropexy in elective repairs, and preferring gastropexy over fundoplication in patients with cardiopulmonary instability requiring emergency repair, all with conditional recommendations.[16](A1)

Differential Diagnosis

The differential diagnosis of PHH includes the following:

• Paraesophageal hiatus hernia Typer III or IV
• Traumatic diaphragmatic hernia
• Gastric diverticulum
• Acute coronary event [17]
• Acute pancreatitis

A thorough clinical investigation, with judicious imaging use, can help differentiate these conditions from PHH and guide management choices.

Prognosis

The overall prognosis of PHH is difficult to assess. The incidence is unknown due to unawareness and a handful of reported cases in the literature. Based on published studies, PHH has a favorable prognosis if treated promptly and has no significant morbidity and mortality postoperatively. Only 1 study has reported a case recurrence out of 8 patients.

Complications

Preoperatively

PHH frequently comes to medical attention when symptomatic and large, potentially with gastric volvulus and incarceration that may result in ischemia and bowel obstruction, depending on the contents of the hernia. Early diagnosis is essential to prevent the strangulation and necrosis of the gastric fundus.[18]

Intraoperatively

Damage to the pleura causing pneumomediastinum is not uncommon after esophageal surgery and usually resolves within 24 hours without any sequelae. Tension pneumothorax is rare (1-2%). Major bleeding has been noticed in 2% of cases. Gastric and esophageal injuries are uncommon (1%). The dead space created within the thoracic cavity following the excision of the sac is eventually reoccupied by the lungs but can also develop a fluid collection (seroma). This fluid collection can get infected, which is more likely if the sac is not excised entirely. These collections can be observed without any intervention if uninfected. Otherwise, interventional radiology-guided drainage and appropriate antibiotics are warranted.[19]