View source for Internal hernia

==Background==
*An internal hernia is the protrusion of bowel through a peritoneal or mesenteric defect within the abdominal cavity, without involvement of the abdominal wall<ref name="pokala">Pokala B, Giannopoulos S, Engwall-Gill A, Tien C, Gould JC, Kindel TL. Prevention and management of internal hernias after bariatric surgery: an expert review. ''Mini-invasive Surg''. 2022;6:23.</ref>
*Historically, '''paraduodenal hernia''' was the most common type; however, with the rise of bariatric surgery, '''post-Roux-en-Y gastric bypass (RYGB) internal hernia''' has become the most commonly encountered form<ref name="takeyama">Takeyama N, Gokan T, Ohgiya Y, et al. CT of internal hernias. ''Radiographics''. 2005;25(4):997-1015. PMID 16009820.</ref>
*Reported incidence after RYGB: '''2–9%''', with higher rates after laparoscopic approaches (fewer adhesions → greater bowel mobility through mesenteric defects)<ref name="chousleb">Chousleb E, Chousleb A. Management of post-bariatric surgery emergencies. ''J Gastrointest Surg''. 2017;21(11):1946-1953. PMID 28900825.</ref>
*'''This is a surgical emergency''' — delayed diagnosis leads to bowel ischemia, necrosis, perforation, and potentially [[Short bowel syndrome|short bowel syndrome]] or death<ref name="pokala"/>

===Classification===
====Post-bariatric (most common in current practice)====
*Three potential hernia spaces are created during RYGB:<ref name="pokala"/>
**Petersen space: Between the Roux (alimentary) limb mesentery and the transverse mesocolon — most common in antecolic approaches
**Jejunojejunostomy (JJ) mesenteric defect: At the enteroenterostomy between the biliopancreatic and alimentary limbs
**Transverse mesocolon defect: Only present in retrocolic Roux limb construction; most common in retrocolic approaches
*Significant weight loss increases risk by creating laxity in the mesentery<ref name="pokala"/>
*Average time from RYGB to internal hernia presentation: '''~2–3 years''', but can occur at any time<ref name="pokala"/>

====Congenital (non-surgical)====
*Paraduodenal (most common congenital type; ~53% of all congenital internal hernias)
**Left paraduodenal (fossa of Landzert) — more common
**Right paraduodenal (fossa of Waldeyer)
*Transmesenteric
*Pericecal
*Foramen of Winslow
*Supravesical / pelvic
*Transomental

==Clinical features==
*Presentation ranges from '''intermittent, vague abdominal pain''' to '''acute surgical abdomen''' — highly variable and often leads to delayed diagnosis<ref name="pokala"/>
*Symptoms may be '''episodic and self-resolving''' (spontaneous reduction of hernia) for weeks to months before an acute presentation

===Classic presentation===
*Postprandial, crampy, periumbilical or left upper quadrant abdominal pain
*Nausea, vomiting
*Abdominal distension
*Obstipation (if complete obstruction)
*Pain may be worsened by eating and improved by position change or lying prone

===Signs of complicated internal hernia (strangulation/ischemia)===
*Severe, constant abdominal pain out of proportion to exam (early ischemia)
*Peritoneal signs (rebound, guarding, rigidity)
*Hemodynamic instability (tachycardia, hypotension)
*Fever, leukocytosis
*Lactic acidosis

===Biliopancreatic limb obstruction (specific to RYGB)===
*May present '''without classic nausea/vomiting or obstipation''' because the obstruction is in the excluded limb<ref name="chousleb"/>
*Instead: left upper quadrant fullness, hiccoughs, unexplained tachycardia
*Left shoulder pain (from gastric remnant distension irritating the diaphragm)
*This is particularly dangerous because the closed-loop obstruction of the biliopancreatic limb can progress to remnant gastric perforation (a catastrophic event that is difficult to diagnose)

===Key ED pearl===
*A post-bariatric surgery patient with intermittent or acute abdominal pain should be presumed to have an internal hernia until proven otherwise
*Multiple ED visits for abdominal pain in a post-RYGB patient without a clear diagnosis is a common pattern preceding internal hernia catastrophe<ref name="pokala"/>

==Differential diagnosis==
*[[Small bowel obstruction]] (adhesive)
*[[Incisional hernia]] (trocar site)
*[[Marginal ulcer]] (anastomotic ulcer)
*Anastomotic stricture
*[[Intussusception]] (at the JJ anastomosis)
*[[Cholelithiasis]] / [[Cholecystitis]] (increased risk after bariatric surgery)
*[[Dumping syndrome]]
*[[Pancreatitis]]
*[[Mesenteric ischemia]]
*[[Appendicitis]]
*[[Nephrolithiasis]]
*Gastric remnant distension/perforation (biliopancreatic limb obstruction)

==Evaluation==
===Workup===
*Determine the type of bariatric surgery performed — this is essential for interpretation of imaging and identification of potential hernia spaces<ref name="pokala"/>
*Labs:
**CBC (leukocytosis suggests ischemia/perforation)
**BMP/CMP (electrolytes, renal function, bicarbonate)
**Lactate — elevated lactate suggests bowel ischemia; however, '''a normal lactate does NOT exclude ischemia or strangulation'''<ref name="chousleb"/>
**Lipase (exclude pancreatitis)
**LFTs
**Coagulation studies
**Type and screen (anticipate possible surgical intervention)
*CT abdomen/pelvis with IV contrast — imaging modality of choice<ref name="iannuccilli">Iannuccilli JD, Grand D, Murphy BL, Evangelista P, Jabbour N, Jamidar PA. Sensitivity and specificity of eight CT signs in the preoperative diagnosis of internal mesenteric hernia following Roux-en-Y gastric bypass surgery. ''Clin Radiol''. 2009;64(4):373-380. PMID 19264181.</ref>
**Oral contrast is not required and may delay imaging
**Obtain with multiplanar reconstructions (coronal and sagittal views are critical)

===Diagnosis===
*CT findings suggestive of internal hernia:<ref name="iannuccilli"/>
**Mesenteric swirl sign (whirlpool sign) — twisting/swirling of the mesenteric vessels and fat; most specific finding
**Small bowel behind the mesenteric vessels (mushroom sign)
**Clustered small bowel loops in the left upper quadrant or in an atypical location
**Jejunojejunostomy (JJ) anastomosis displaced to the right of midline or above the transverse colon
**Small bowel obstruction with transition point at a mesenteric defect
**Engorgement or stretching of mesenteric vessels
**Hurricane eye sign — rounded configuration of distal mesenteric fat and vessels
*CT sensitivity is imperfect: Reported sensitivity ranges from '''63–80%'''; specificity ~76%<ref name="iannuccilli"/>
**Retrospective review shows diagnostic abnormalities present in up to 97% of cases, but these are frequently missed prospectively by general radiologists
**If clinical suspicion is high and CT is equivocal or negative, surgical exploration is still indicated<ref name="pokala"/>
*Communicate directly with the radiologist — alert them to the bariatric surgical history and ask them to specifically evaluate for internal hernia; this significantly improves diagnostic accuracy<ref name="pokala"/>
*Upright abdominal XR: May show dilated loops or air-fluid levels but is insufficient to diagnose or exclude internal hernia; '''CT is mandatory'''
*Congenital internal hernias are typically diagnosed on CT in the setting of small bowel obstruction without prior surgical history

==Management==
===ED management===
*NPO
*IV fluid resuscitation — crystalloid bolus; correct dehydration and electrolyte abnormalities
*IV antiemetics (ondansetron)
*IV analgesia — do not withhold pain control; opioids as needed
*Nasogastric tube: Consider for decompression if significant vomiting or distension
*Broad-spectrum antibiotics: Initiate if concern for ischemia, perforation, or sepsis (e.g. piperacillin-tazobactam or cefepime + metronidazole)
*Lactate monitoring: Serial measurements; rising lactate is ominous

===Surgical management===
*'''Emergent surgical consultation''' for all suspected internal hernias — this is a '''time-sensitive surgical emergency'''<ref name="chousleb"/>
*Laparoscopic exploration is preferred when performed by an experienced bariatric surgeon; may require conversion to open in complicated cases<ref name="pokala"/>
*Surgical goals:
**Reduce herniated bowel
**Assess bowel viability (resect necrotic segments)
**Close mesenteric defects with non-absorbable suture to prevent recurrence
*If bowel ischemia has progressed to necrosis → segmental resection; extensive resection may result in [[Short bowel syndrome|short bowel syndrome]]
*'''Contact the patient's bariatric surgeon''' if possible — they know the specific anatomy and prior operative details
*If a bariatric surgeon is not available at the presenting facility, consult general surgery and arrange transfer to a bariatric center if the patient can be stabilized<ref name="pokala"/>

===Critical management pearl===
*'''Do NOT discharge a post-bariatric surgery patient with unexplained abdominal pain and a negative or equivocal CT''' without surgical consultation — internal hernias can spontaneously reduce and appear normal on imaging, only to recur and strangulate<ref name="pokala"/>

==Disposition==
*Operative:
**All patients with CT findings consistent with internal hernia
**All patients with clinical concern for ischemia or strangulation regardless of CT findings
**Biliopancreatic limb obstruction with gastric remnant distension
*Admit with surgical consultation:
**Equivocal CT findings in a symptomatic post-RYGB patient
**Resolved symptoms but history concerning for intermittent internal hernia (may require elective/semi-urgent laparoscopic exploration)
*Transfer:
**If bariatric surgical expertise is not available at the presenting facility, stabilize and transfer to a facility with bariatric surgery capability
*Discharge is rarely appropriate for post-RYGB patients with significant abdominal pain:
**If pain fully resolves, CT is clearly negative, labs are normal, and the patient tolerates oral intake, discharge may be considered with '''very close follow-up''' (24–48 hours with bariatric surgeon)
**Provide strict return precautions: worsening pain, vomiting, inability to eat, fever
**Document the discussion of the risk of intermittent internal hernia and the possibility that imaging may be falsely negative

==See also==
*[[Bariatric surgery complications]]
*[[Small bowel obstruction]]
*[[Gastric bypass surgery]]
*[[Dumping syndrome]]
*[[Mesenteric ischemia]]
*[[Short bowel syndrome]]
*[[Marginal ulcer]]
*[[Incisional hernia]]

==External links==
*[https://www.oaepublish.com/articles/2574-1225.2021.136 Prevention and management of internal hernias after bariatric surgery: an expert review - Mini-invasive Surg 2022]
*[https://pubmed.ncbi.nlm.nih.gov/28900825/ Management of post-bariatric surgery emergencies - J Gastrointest Surg 2017]
*[https://pubmed.ncbi.nlm.nih.gov/19264181/ Sensitivity and specificity of CT signs for internal hernia after RYGB - Clin Radiol 2009]
*[https://pubmed.ncbi.nlm.nih.gov/16009820/ CT of internal hernias - Radiographics 2005]
*[https://appliedradiology.com/articles/imaging-of-postoperative-internal-hernias Imaging of postoperative internal hernias - Applied Radiology]

==References==
<references/>

[[Category:GI]] [[Category:Surgery]]