Abdominal Imaging

ª Springer Science+Business Media, LLC 2010 Published online: 16 May 2010

Abdom Imaging (2011) 36:126–129 DOI: 10.1007/s00261-010-9626-4

Petersen’s hernia as a complication of bariatric surgery: CT findings M. A. S. Ximenes, R. H. Baroni, R. M. C. Trindade, M. C. J. Racy, A. Tachibana, R. A. Moron, M. B. G. Funari Radiology, Hospital Israelita Albert Einstein, Sao Paulo, Brazil

Abstract Referrals for bariatric surgery have currently increased due to the need for more effective interventions in the management of severely obese patients. The Roux-en-Y gastric bypass is currently one of the preferred procedures, and internal hernias are the main causes of late postoperative complication. Petersen’s hernia is a less common finding in most published papers compared to transmesocolic hernia, however, it seems to be increasing in incidence (in our service, eight cases which have been tomographic diagnosed in 2 years, were confirmed by laparoscopic surgery). The clinical findings are not specific, usually with abdominal pain, associated or not with abdominal distention and vomiting. In this context, imaging exams have an important role in the early diagnosis and surgery of this condition, with multislice computed tomography being the most accurate method. The aim of this pictorial essay is to the demonstrate the main CT findings associated with Petersen’s hernia in patients who underwent Roux-en-Y gastric bypass. Key words: Petersen’s hernia—Internal hernias—Bariatric surgery—Petersen’s space—Roux-enY gastric bypass complications

The Roux-en-Y gastric bypass To understand the most common complications of bariatric surgery, it is essential for the abdominal radiologist to be familiar with the different surgical techniques. The Roux-en-Y gastric bypass is currently one of the

Correspondence to: M. A. S. Ximenes; email: mauricioximenes@ gmail.com

preferred procedures for morbid obesity. The minimum amount of gastrointestinal tract that is excluded from intestinal transit is the distal stomach, the duodenum, and about 40 cm of the proximal jejunum (afferent or biliopancreatic loop). The standard Roux loop measures about 75 cm. The upper pouch is made horizontally or vertically, and has a capacity of about 15–25 mL; the distal stomach is separated or fully excluded. An anastomosis (proximal anastomosis) is made between this small pouch and part of the jejunum (feeding loop) that was sectioned close to its origin [1]. The afferent or biliopancreatic loop starts from the remaining stomach, passing along the duodenum until the proximal jejunum, in which the jejuno-jejunal anastomosis (distal anastomosis) is performed. The anastomotic loop may be retrocolic or antecolic. The retrocolic anastomosis creates a potential space in the mesentery, opening the possibility of a transmesenteric hernia [2]. Petersen’s hernia may occur in both types of anastomosis [1, 3]. The scheme in Fig. 1 explains the surgical procedure.

Petersen’s hernia Petersen’s hernia is a specific type of internal hernia in which the intestine moves into a potential space between the caudal surface of the transverse mesocolon and the mesentery of the Roux limb (Petersen’s space). As mentioned before, it may occur in both types of anastomosis (antecolic or retrocolic). Although Petersen’s hernia occurs in a potential space behind the Roux limb, its clinical presentation and most of the imaging findings are similar to those of other internal hernias (Fig. 2). In our experience, most cases occurred about 1 year after bariatric surgery. Other investigators showed that there is marked temporal variability between surgery and the occurrence of internal hernias [1]. Rapid and marked weight loss appears to be a contributing factor for opening potential spaces through which hernias may occur.

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Fig. 1. The Roux-en-Y gastric bypass surgical procedure: GP gastric pouch, MC mesocolon, FL feeding loop, BPL biliopancreatic loop.

CT findings There are certain imaging findings in patients who have undergone Roux-en-Y gastric bypass bariatric surgery that suggests an internal hernia, some of which are more specific for the diagnosis of a hernia in Petersen’s space. The main points to observe are the presence and site of abdominal distention, the herniated intestinal loop segment, the presence of mesenteric vessel rotation and mesenteric fat haziness, the position of the Treitz angle and the course of the ileum.

Mesenteric swirl and mesenteric fat haziness

Fig. 2.

Arrow showing Petersen¢s space.

Mesenteric vessel rotation, described as the whirl sign or mesenteric swirl, and mesenteric fat haziness are usually seen (Fig. 3A, B). This finding has been shown in various articles to be the most sensitive sign for the diagnosis of internal hernias [4, 5], but is not specific.

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Fig. 3. A, B Abdominal CT with oral and intravenous contrast medium. Observe rotation of mesenteric vessels (‘‘whirl sign’’), accompanied by mesenteric fat haziness.

Fig. 6. A, B Abdominal computed tomography with oral and intravenous contrast medium: white arrows herniated intestinal segment (‘‘mushroom-like’’ aspect), black arrows mesenteric vessel stretching and engorgement.

Fig. 4. A, B Abdominal computed tomography with oral and intravenous contrast medium: black arrows gastrojejunal anastomosis, white arrows distended herniated loop, arrowheads excluded stomach.

Fig. 7. Abdominal computed tomography with oral and intravenous contrast medium: white arrows mesenteric vessel stretching and engorgement, black arrow jejuno-jejunal anastomosis, arrowhead herniated loop. Doted white arrows enlargement of peritoneal lymph nodes, and mesenteric haziness. Fig. 5. Abdominal computed tomography with oral and intravenous contrast medium: white arrows herniated loop, arrowheads excluded stomach.

Intestinal distention in the upper abdomen An important parameter to be evaluated is the pattern of intestinal loop distension, usually a mild distension of small intestine loops in the upper abdomen, in most cases located preferentially in the left hypochondrium (Fig. 4A, B).

Fig. 8. A, B Abdominal CT with oral and intravenous contrast medium, in two different patients. Note that the ligament of Treitz is displaced anteriorly and to the right.

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Fig. 9. A/E Abdominal CT with oral and intravenous contrast medium. Axial (A–C) and oblique coronal reconstruction (D, E) images showing the ileal course. Table 1. MDCT findings Rotation of mesenteric vessels (whirl sing) Mesenteric fat haziness Intestinal distention in the upper abdomen Herniated intestinal loop above the gastric level Treitz angle displaced anteriorly and to the right Middle/distal ileum courses downwards from the left hypochondrium

Herniated intestinal loop above the gastric level A key finding for tomographically diagnosing the herniated segment is the presence of a jejunal loop located above the stomach (Fig. 5). A distended jejunal loop above the gastric level is usually accompanied by mesenteric vessel stretching and engorgement, and mesenteric vessel elongation [4–6]; in a coronal reconstruction, with herniated loops in the upper pole, these findings have a mushroom-like appearance (Fig. 6A, B). Sometimes adjacent peritoneal lymph nodes are enlarged (Fig. 7). Lockhart et al. [5] also described this finding, which increases the diagnostic specificity.

Treitz angle displaced anteriorly and to the right A further finding is the position of the Treitz angle, that is usually displaced anteriorly and to the right (Figs. 8A, B).

Middle/distal ileum courses downwards from the left hypochondrium Middle ileal segments have a descending trajectory from the left upper quadrant towards the right lower quadrant, and the distal ileum has a horizontal path up to the cecum (Fig. 9A–E). Some signs, such as distended intestinal loops, the whirl sign and the mushroom-like appearance are common to other types of internal hernias. A precise diagnosis of Petersen’s hernia requires specifically finding and localizing the herniated intestinal segment. The main CT findings in Petersen’s hernia are shown in Table 1. References 1. Labrunie EM, Marchiori E (2007) Obstruc¸a˜p intestinal po´s-gastroplastia redutora pela te´cnica de Higa para tratamento da obesidade mo´rbida: aspectos por imagem. Radiologia Brasileira 40(3):161–165 2. Reddy SA, Yang C, McGinnis LA, et al. (2007) Diagnosis of transmesocolic internal hernia as a complication of retrocolic gastric bypass: CT imaging criteria. AJR 189:52–55 3. Blachar A, Federle MP, Pealer KM, et al. (2002) Gastrointestinal complications of laparoscopic Roux-en-Y gastric bypass surgery: clinical and imaging findings. Radiology 223:625–632 4. Takeyama N, Gokan T, Ohgiya Y, et al. (2005) CT of internal hernias. Radiographics 25:997–1015 5. Lockhart ME, Tessler FN, Canon CL, et al. (2007) Seven signs after gastric bypass. AJR 188:745–750 6. Higa KD, Ho T, Boone KB, et al. (2003) Internal hernias after laparoscopic Roux-en-Y gastric bypass: incidence, treatment and prevention. Obesity Surgery 13:350–354