Acquired interstitial hernia

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An interstitial hernia has a hernial sac which is located between the layers of the anterior abdominal wall. An inguinal form was first described as early as 1661 by the Danish physician Thomas Bartholin1 and while quite rare, representing an estimated 0.07% of all hernias, it is associated with a high risk of incarceration and strangulation.2
A 72‐year‐old man underwent an elective open right hemicolectomy for a caecal tumour found on colonoscopy and confirmed to be an adenocarcinoma on biopsy. Staging computed tomography (CT) of the chest, abdomen and pelvis was suggestive of abdominal wall involvement, with no evidence of distant metastases (Fig. 1). His past medical history included open appendicectomy, transient ischaemic attacks and hepatitis C infection. Preoperative blood tests were unremarkable and his antiplatelet therapy, which consisted of clopidogrel, was held for 7 days prior to the resection.
At laparotomy, the caecal tumour was confirmed to involve the anterolateral abdominal wall as well as the overlying omentum. The liver appeared normal. En bloc mobilization and resection of the right colon and tumour was undertaken including the inner two muscle layers of the abdominal wall and part of the omentum. The defect in the abdominal wall was too big to close primarily; however, the exposed muscle layers were densely adherent with no visible gaps between them and the external oblique muscle was intact. The right hemicolectomy was completed with a side‐to‐side stapled anastomosis followed by a saline washout and standard midline fascial closure of the abdomen.
The patient's early recovery was complicated by what was initially suspected to be post‐operative ileus. He experienced increasing abdominal distension and ongoing nausea, with several large vomits on the third post‐operative day. On examination, his abdomen was distended, tense and generally tender to palpation. A nasogastric tube was inserted and a CT scan of his abdomen and pelvis was arranged.
The CT images revealed herniation of a small bowel loop into the space between external and internal oblique muscle layers at the site of the surgically created abdominal wall defect (Fig. 2). The proximal small bowel was distended and filled with fluid, in keeping with an obstruction. He underwent relaparotomy, at which the CT findings were confirmed and an incarcerated loop of ileum was reduced.
The hernial defect was a gap between the external and internal oblique muscle layers over a 12‐cm length. All of the free edges of exposed muscle were overrun, tension‐free, with a polyglactin suture and then sutured down to the intact external oblique muscle layer. No bowel resection was required. The patient was discharged from the surgical ward on post‐operative day 27 for a further 1 week of inpatient rehabilitation, prior to going home. Follow‐up CT did show a recurrence of his interstitial hernia which remains asymptomatic.
This case illustrates an uncommon example of an iatrogenic interstitial hernia. Acquired interstitial hernias may be caused by abdominal wall trauma or surgical incisions. Congenital interstitial hernias have also been described, including occurrence associated with abnormal descent of a testicle in children,3 or an unusual presentation of an adult inguinal hernia.2 Previous case reports of post‐operative acquired interstitial hernias have included Lichtenstein mesh repair of inguinal hernia, open appendicectomy, caesarean section via a Pfannenstiel incision, laparoscopic port site incision, open cholecystectomy, open nephrectomy and a colostomy closure site.4
Clinical diagnosis of an interstitial hernia may be quite challenging and usually requires CT imaging for confirmation, and it should be considered in patients complaining of ongoing pain at previous abdominal incision sites, or suspected post‐operative bowel obstruction.
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