British Journal of Radiology (2005) 78, 796-802
© 2005 British Institute of Radiology
doi: 10.1259/bjr/87050272
Congenital internal hernia as a cause of small bowel obstruction: CT findings in 11 adult patients
R Zissin, MD
1,5
M Hertz, MD
2,5
G Gayer, MD
3,5
H Paran, MD
4,5 and
A Osadchy, MD
1,5
Departments of 1 Diagnostic Imaging and 4 Surgery "A", Meir Hospital, Sapir Medical Center, Kfar-Saba, and the Departments of Diagnostic Imaging, 2 Chaim Sheba Medical Center, Tel Hashomer, Tel Aviv, and 3 Assaf Harofe Medical Center, Zrifin, affiliated to the 5 Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
Correspondence: Dr R Zissin, Department of Diagnostic Imaging, Sapir Medical Center, Kfar Saba, 44281, Israel
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Abstract
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The aim of this study is to report the CT findings in patients proved to have congenital internal hernia (CIH) as a cause of small bowel obstruction (SBO). The CT scans of 11 patients (9 men and 2 women, with ages ranging from 20 years to 95 years (mean 60.7 years), presenting with clinical symptoms and signs of SBO without previous abdominal surgery or trauma, were retrospectively reviewed. In all patients features of SBO were seen. In addition, in nine of them a saclike mass, containing dilated small bowel loops with mesenteric vessels converging toward its orifice was demonstrated and a pre-operative diagnosis of an incarcerated internal hernia was suggested. In the other two, a closed loop obstruction was seen without an identifiable cause. Mural thickening of the entrapped loops within the hernial sac was seen in five patients, with hypoperfusion in four of them, blurring of the mesenteric vessels with localized mesenteric fluid was demonstrated in seven and free peritoneal fluid in 10. All patients were operated on following the CT and an incarcerated CIH was confirmed. Gangrenous bowel was present at exploration in seven cases. One patient died. In conclusion, in patients with intact abdomen and SBO, CT may be the first imaging modality to discover a clinically unsuspected CIH, which requires prompt surgical intervention. Radiologists should be aware of the CT features suggestive of a SBO caused by CIH, i.e. a saclike mass of dilated small bowel loops, as a correct diagnosis will influence patient management and prognosis.
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Introduction
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An internal hernia is defined as the protrusion of a viscus through a normal or abnormal opening within the boundaries of the peritoneal cavity. The autopsy incidence of internal hernias is 0.2–2%, most of them asymptomatic [1–5]. The hernial orifice may be a pre-existing anatomic structure, such as the foramen of Winslow, or a pathological defect of congenital or acquired origin. Internal hernia is an infrequent cause of small bowel obstruction (SBO) with a reported incidence of up to 5.8% of all cases of intestinal obstruction, and paraduodenal hernias representing 50% of the 500 cases published up to the year 2000 [1, 6]. Despite the congenital origin, a congenital internal hernia (CIH) is diagnosed more frequently in adulthood, with a mean age of 38 years at diagnosis [1, 6–8]. A pre-operative diagnosis of an incarcerated CIH is often difficult to establish due to non-specific symptoms and signs. Such an obstruction, however, may be associated with high morbidity and mortality because of both the increased risk of strangulation and the delay in the correct diagnosis and surgical treatment [1–6].
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Materials and methods
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Between 1 November 2003 and 30 November 2004 we examined nine consecutive patients with SBO caused by CIH which had been identified on CT pre-operatively and proven at surgery. We have included two additional patients with the same condition who had been diagnosed before this period, and these 11 patients comprise our study group. There were nine men and two women with ages ranging from 20 years to 95 years (mean age 60.7 years). Their clinical data and imaging studies were retrospectively reviewed and the CT findings are described in detail. No patient had a history of previous abdominal surgery or trauma nor a significant abdominal inflammatory condition. Two patients have been described previously in detail as case reports [12, 13].
CT scans were obtained on a Picker Mx Twin-flash (helical scanner). Our protocol for suspected SBO included the following:
- Scanning with 6.5–8.8–10 mm collimation and 6–8 mm interval from the diaphragm to the symphysis pubis.
- Administration of 800 ml orally diluted water-soluble contrast material, over 2 h before the examination and an additional 250 ml just before the study.
- Intravenous injection of 80–100 cm3 of non-ionic contrast of Ultravist 300 (Iopromide; Schering AG, Berlin, Germany) by bolus or using a power injector, at a rate of 1.5 ml s–1 with scanning delay time of 70 s after the start of the injection.
The abdominal CT studies of the patients were retrospectively reviewed for the following signs:
- Characteristic findings of SBO of discrepancy in the calibre of small bowel loops between proximal dilated (>2.5 cm in diameter) and collapsed loops more distally and the presence of small bowel faeces sign.
- The presence and location of an encapsulated cluster of dilated small-bowel loops with a saclike appearance, representing an internal hernia, with mesenteric vessels converging toward its entrance.
- The presence of suggestive signs of bowel ischaemia: bowel wall thickening, hypo/non-enhancing bowel wall, blurring of the mesenteric vessels with localized mesenteric fluid, pneumatosis intestinalis, free intraperitoneal fluid [10, 11].
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Results
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All patients presented with a painful swollen abdomen, associated with nausea and vomiting in seven. Two patients had fever up to 39°C. Physical examination revealed abdominal distension in all, with diffuse or pelvic tenderness in eight patients and signs of peritoneal irritation in four. Laboratory examination revealed a leukocytosis with a range of 12 000–20 000 cells mm–3 in eight patients. Blood gases taken in three patients pre-operatively were normal.
Findings at CT were (Table 1
) a saclike mass containing dilated small bowel loops with engorged mesenteric vessels converging toward its entrance in nine patients. The entrapped dilated loops within the hernia were un-opacified, and fluid-filled in eight patients. The type of internal hernia in these nine patients was classified according to the location of the saclike mass: transmesenteric (Figures 1 and 2) in five patients, paracaecal (Figures 3 and 4) in two, and paraduodenal (Figure 5) and paravesical (Figure 6) in one patient each. A transmesenteric hernia was defined as a pseudosac containing dilated small bowel loops pushed against the abdominal wall with no overlying omental fat and displacing the nearby colon. It was either a right-sided transmesenteric hernia (n=4) situated in the right abdomen sub-hepatically, displacing the ascending colon medially (Figure 1), or a left-sided one (n=1) seen in the left upper abdomen displacing the transverse colon posteriorly (Figure 2). A paracaecal hernia was diagnosed when an encapsulated cluster of dilated small-bowel loops were found adjacent to a displaced caecum (Figures 3 and 4), paraduodenal when a saclike mass with encapsulation was interposed between the stomach and the pancreas with displacement of the superior mesenteric trunk (Figure 5), and paravesical when a pseudosac was seen adjacent to the urinary bladder (Figure 6).
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Figure 1. A 91-year-old man presented with small bowel obstruction (SBO) and diffuse abdominal tenderness. (a) Contrast enhanced CT at the mid abdomen shows a conglomerate of dilated, unopacified, fluid-filled small bowel loops (SB), in the subhepatic region (L=liver), displacing the ascending colon (white arrow) medially. The dilated loops show mural thickening (black arrow) with relative hypoperfusion and adjacent free peritoneal fluid (F), features suggesting strangulation. Dilatation of proximal, opacified small bowel loops is also seen. (b) More caudally, the cluster of dilated small bowel loops with thickened wall is demonstrated adjacent to the right abdominal wall with no overlying omental fat. Engorged and blurred mesenteric vessels, with adjacent mesenteric fluid, are seen converging toward the orifice (arrow) of the hernia sac. A pre-operative CT diagnosis of an incarcerated, strangulated transmesenteric internal hernia was confirmed on surgery. At laparotomy, resection of 50 cm of necrotic jejunum with end to end anasomosis and repair of the hernia were performed.
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Figure 2. A 95-year-old man presented with small bowel obstruction (SBO) and diffuse abdominal tenderness. (a) Contrast enhanced CT at the mid abdomen shows a cluster of dilated, unopacified, fluid-filled small bowel loops (thin black arrows) with converging mesenteric vessles (black arrow), in the left abdomen adjacent to the left abdominal wall with no overlying omental fat, displacing the transverse colon posteriorly (white arrowheads) and medially. The dilated loops show mural thickening with relative hypoperfusion with adjacent mesenteric fluid suggesting strangulation. (b) More caudally, the conglomerate of dilated small bowel loops with a thickened wall, some with the small bowel faeces sign (black arrows), are seen displacing the proximal transverse colon (arrowhead). Blurred and engorged mesenteric vessels are seen, converging toward the orifice of the hernia sac (white arrows) as well as free peritoneal fluid. A pre-operative CT diagnosis of an incarcerated, strangulated transmesenteric internal hernia was confirmed on surgery.
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Figure 3. A 76-year-old man presented with small bowel obstruction (SBO). Contrast-enhanced CT at the right lower abdomen shows a saclike mass of unopacified dilated small bowel loops with the small bowel faeces sign (small white arrows) and mesenteric vessels converging toward its orifice (arrowhead). The "sac" is interposed between the anteromedially displaced cecum (C) with the entrance of the terminal ileum (thick white arrow) and the lateral abdominal wall. Proximal dilated opacified loops are seen. At surgery a hernia sac containing 60 cm of viable jejunum was found behind the cecum. The incarcerated bowel was reduced and the hernia orifice was sutured.
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Figure 4. A 44-year-old woman presented with small bowel obstruction (SBO) and fever. (a) Contrast-enhanced CT at the right lower abdomen shows a cluster of unopacified dilated small bowel loops (white arrows), medially to the cecum with the terminal ileum (black arrow). Opacified, dilated small bowel loops proximal to the hernia sac are also seen. (b) Lower down, the nature of the saclike mass with the unopacified, dilated small-bowel loops with converging and blurred mesenteric vessels (black arrow), interposed between the laterally displaced cecum and the abdominal wall, is clearly demonstrated. At surgery a paracecal hernia containing a viable closed loop was found and repaired.
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Figure 5. A 48-year-old man presented with small bowel obstruction (SBO) due to left paraduodenal hernia. (a) Contrast-enhanced CT at the mid left abdomen demonstrates dilatation of clustered small-bowel loops (small white arrows) with converging mesenteric vessels (white arrow), causing right displacement of the superior mesenteric vessels (arrowhead). Mild left-sided hydronephrosis is also seen, as well as the small bowel faeces sign within the dilated loop (black arrow) (Reprinted with permission [12]). (b) CT section at a lower level shows the cluster of dilated small bowel loops (black arrows) causing asymmetrical bulging of the left abdominal wall. The engorged and crowded mesenteric vessels are seen converging toward the opening of the hernia sac (white arrows). Note the excreted contrast media within the right ureter with its absence on the left side related to the uro-mechanical disturbance (Reprinted with permission [13]). At surgery, a hernia sac, containing viable loops of almost the entire small intestine, was found in the left upper quadrant with the inferior mesenteric vein at its opening. Hernial repair was performed.
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Figure 6. An 80-year-old man presented with nausea and vomiting with diffuse abdominal tenderness. (a) Contrast-enhanced CT at the pelvis shows numerous dilated small bowel loops (black arrows) one of them with a transition zone (long white arrow) as well as collapsed distal loops (thick white arrow). (b) 1.3 cm caudally, another transition zone of a dilated loop is seen adjacent to that seen in (a) (white arrow) compatible with an entrapped loop within an internial hernia. (c) At the level of the urinary bladder (B), the thickened-wall of the incarcerated small bowel loop is clearly demonstrated (arrows) with adjacent fluid and mesenteric fat infiltration. At laparotomy, a gangrenous incarcerated ileal loop was found within a paravesical hernia. Small bowel resection with ileo-ileal anastomosis and hernial repair were performed.
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Dilatation of proximal loops, opacified with the orally ingested contrast, was noted in all, involving only several proximal loops in the case of the incarcerated paravesical hernia. The transit zone between dilated to collapsed loops was seen at the hernia orifice in eight patients.
In two patients, radial distribution of dilated small bowel loops located centrally within the abdominal cavity with convergence of mesenteric vessels was seen, suggestive of a closed loop obstruction without an identifiable organic cause at the transition zone (Figure 7). As these patients had not been operated on before, and in the absence of any certain obstructing lesion, the presumed diagnosis was of SBO due to either an internal hernia or a congenital band.
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Figure 7. A 43-year-old man presented with small bowel obstruction (SBO) and fever with diffuse abdominal tenderness. (a) Contrast enhanced CT at the mid-abdomen shows dilated small bowel loops and engorged and twisted mesenteric vessels (arrow) with a whirl pattern indicating volvulus. (b) More caudally, note the radial distribution of the dilated loops and convergence of engorged mesenteric vessels (arrow) suggesting a closed loop SBO. At laparotomy, viable loops were found within an internal hernia, but its distinct type could not be established. The hernia was repaired.
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The small bowel faeces sign was present in seven patients (Figures 2, 3 and 5
). Bowel wall thickening of loops entrapped within the hernial sac was seen in five patients (Figures 1, 2 and 6) with hypoperfusion of the dilated segments (Figures 1 and 2) in four. All five patients were found to have a gangrenous bowel segment at exploration. Blurring of the mesenteric vessels with localized mesenteric fluid was demonstrated in seven patients (Figures 1, 4 and 6), a necrotic bowel segment was found in six at laparotomy. Free peritoneal fluid was present in 10. The fluid was contained in the pelvis in three patients and extended outside the pelvis in seven. The amount of free fluid did not correlate with intestinal necrosis, as even the three patients with only a small amount of fluid proved to have gangrenous bowel.
Eight patients underwent operation immediately following the CT with a suggestive diagnosis of an obstructing internal hernia in six of them and a differential diagnosis of an obstructing internal hernia or congenital band in the other two. Three patients were operated on the following day after review and revision of the CT, with a pre-operative diagnosis of an obstructing internal hernia.
Laparotomy revealed incarceration of small bowel loops within mesenteric defects in all. Reduction of the hernia content and correction of the anatomical defect, which had led to the herniation was performed. Gangrenous bowel was present in seven patients (two of them had a delay in the surgical intervention performed following revision and correction of the CT diagnosis) with resection of the necrotic segment and primary anastomosis. In two patients with proven bowel necrosis, in whom blood gases were tested prior to the operation, no metabolic acidosis was found.
10 patients recovered uneventfully while the oldest patient, a 95-year-old male, died 11 days following surgery with multi-organ failure.
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Discussion
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A CIH results from congenital anomalies of intestinal rotation and peritoneal attachment [1–5]. CIH may be classified according to their location into, in decreasing order of frequency, paraduodenal, pericaecal, transmesenteric, intersigmoid and paravesical hernias [14]. The size of the sac, the length of the incarcerated bowel loops and the formation of interloops adhesions, all increase with age, explaining the appearance of SBO later in life, although CIH is a congenital condition [6]. Although left paraduodenal hernias are reported to be more common than other types of CIH, there was only one such patient in our series. We assume that as left paraduodenal hernia more often causes intermittent symptoms with spontaneous reduction and is less frequently present with SBO, examination of the patient in a symptom-free period would probably be falsely negative and the diagnosis is therefore more difficult and less likely to be made [2].
CIH is, although rare, an important cause of SBO, and its diagnosis is a challenge for both physicians and radiologists. Obstructing CIHs have usually been published as case reports or small case series, while larger series include both congenital and acquired internal hernias [3, 4, 8]. A history of chronic, intermittent attacks of vague abdominal discomfort or cramps without previous surgery may be suggestive of the diagnosis. The pain is often associated with abdominal distention and vomiting, is usually post-prandial and worsens with eating [1]. In one of our patients with SBO due to a left paraduodenal hernia, the non-complicated hernia was retrospectively recognized on a previous CT performed a few months earlier for non-specific abdominal complaints [13].
Nowadays, the advantages of CT have led to an increased role in patients suspected of having SBO, both in the initial diagnosis and as guidance for management. CT has a high diagnostic accuracy not only in detecting SBO but also in defining its severity and aetiology [9–11]. The latter is determined by meticulous analysis of the transition zone between dilated and collapsed loops, allowing for the correct diagnosis of the cause of the obstruction in 73–95% of cases [9–11].
Regarding the differential diagnosis of SBO, adhesions caused by previous abdominal operations account for up to 80% of cases, followed by hernias in 2–8% [7, 9, 10]. In patients with clinically suspected SBO and with neither previous abdominal operations nor an identifiable incarcerated external hernia, the differential diagnosis includes miscellaneous entities that can often be inferred from the CT findings [7, 9, 10]. These aetiologies include undiagnosed Crohn's disease obstructing the small bowel, an incarcerated femoral or obturator hernia, an obstructing phytobezoar (that may appear in patients with inadequate chewing, diabetic gastroparesis or an excessive vegetarian diet), gallstone ileus (which may occur in elderly women with known gallstones), obstructing neoplasms and CIH [7, 9, 10, 15, 16].
To our knowledge our series is the largest reported of intestinal obstruction caused by CIH. Although the CT features of this condition are not pathognomonic, the combination of CT findings together with an intact abdomen on inspection and palpation aids in establishing the correct diagnosis. For example, a cluster of dilated small bowel loops lying adjacent to the abdominal wall, without overlying omental fat, and causing displacement of the nearby colon centrally, is regarded as a distinctive feature of a transmesenteric internal hernia [1, 3, 4]. Alternatively, an encapsulated cluster of dilated small-bowel loops interposed between the pancreas and stomach to the left of the ligament of Treitz, causing a mass effect on the posterior stomach wall, on the duodenojejunal junction and on the transverse colon with displacement of the main mesenteric trunk to the right and sometimes with mild left-sided hydronephrosis, suggest an incarcerated left paraduodenal hernia [1, 13]. Clustered and dilated small bowel loops seen lateral and inferior to the second part of the duodenum suggest a right-sided paraduodenal hernia [2, 14]. Similarly, the demonstration of a saclike mass of dilated small bowel loops in different locations within the abdominal cavity with engorged mesenteric vessels converging toward the entrance of the hernia sac can be indicative of other types of CIH [1, 2, 12, 14].
Because of the increased risk of bowel entrapment within the hernia sac with acute strangulation and bowel infarction, even a small CIH is dangerous, and prompt diagnosis and treatment are required. Seven out of our 11 patients (63.6%) were found to have a strangulating obstruction with bowel necrosis. The CT findings suggestive of bowel ischaemia included mural thickening seen in five of these seven patients, with hypoperfusion in four of them, blurring of the mesenteric vessels with localized mesenteric fluid in six patients and free peritoneal fluid seen in all [9–11]. The amount of peritoneal fluid, though, did not correlate with the presence of gangrenous bowel. Furthermore, none of the patients had other more suggestive CT findings of bowel infarction such as pneumatosis intestinalis, gas in the portal vein or lack of enhancement of the bowel wall. It should be noted that our CT protocol, regarding the rate of intravenous contrast injection and the slice collimation, is not ideal for modern multidetector CT (MDCT) scanners. Nowadays, the improvement in CT technology by the introduction of MDCT, with thinner overlapping sections enabling multiplanar reformatting may be extremely useful in the diagnosis of CIH. Additionally, the use of oral contrast is still a subject of debate; although it might add useful information with regard to the degree of obstruction, it can also reduce the sensitivity of the technique for evaluating the intestinal wall [9].
The small bowel faeces sign found within dilated, obstructed loops was demonstrated in seven patients (63.6%). This finding is most often related to a SBO, reported recently in 55.9% of cases of SBO, most often in patients with moderate and high degrees of obstruction [17].
To conclude, as CT is frequently used to evaluate patients with SBO, it may enable the diagnosis of an unsuspected CIH to be made as the cause of the obstruction. Such a condition may be life threatening, requiring prompt management, and a correct diagnosis is crucial. Radiologists should be alerted to the probability of a CIH-related SBO, in the proper clinical setting of an adult patient presenting with SBO without previous abdominal surgery or trauma and with no incarcerated external hernia. CT findings of abnormal encapsulation of small bowel loops in addition to characteristic features of SBO should suggest the diagnosis.
Received for publication January 23, 2005.
Revision received March 19, 2005.
Accepted for publication April 15, 2005.
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Abstract
Introduction
