Multiple giant diverticula of the jejunum causing intestinal obstruction: report of a case and review of the literature
© Falidas et al; licensee BioMed Central Ltd. 2011
Received: 9 December 2010
Accepted: 8 March 2011
Published: 8 March 2011
Multiple diverticulosis of jejunum represents an uncommon pathology of the small bowel. The disease is usually asymptomatic and must be taken into consideration in cases of unexplained malabsorption, anemia, chronic abdominal pain or discomfort. Related complications such as diverticulitis, perforation, bleeding or intestinal obstruction appear in 10-30% of the patients increasing morbidity and mortality rates. We herein report a case of a 55 year-old man presented at the emergency department with acute abdominal pain, vomiting and fever. Preoperative radiological examination followed by laparotomy revealed multiple giant jejunal diverticula causing intestinal obstruction. We also review the literature for this uncommon disease.
Multiple diverticulosis of the jejunum constitutes an uncommon pathology of the small bowel. The disease is often asymptomatic and must be taken into consideration in cases of unexplained malabsorption, anemia, chronic abdominal pain and discomfort. Related complications such as diverticulitis, hemorrhage, obstruction and perforation present high mortality and morbidity rates. We herein report a case of a 55 year-old man presented at the emergency department because of acute abdominal pain, vomiting and fever. Preoperative radiological examination followed by laparotomy revealed multiple and giant jejunal diverticula causing intestinal obstruction. We also review the literature for this uncommon disease.
A 55-year old man arrived at the emergency department complaining of 48-hour lasting intense abdominal pain and vomiting. The patient had a free medical history and was not receiving any drugs at that time. He mentioned a two-year-lasting remittent abdominal pain, fullness and often abdominal distension. The patient also mentioned a particular intolerance of pulse and vegetables.
The patient's post operative course was uneventful. Pathology report described large diverticula and rare focus of diverticulitis. During 24-months follow-up, the patient was symptoms free.
Diverticulosis of the small bowel is a rare disease with variable clinical presentations and often incidentally discovered during radiological investigations. The disease was first described by Sommering in 1794 and later by Astley Cooper in 1809. Gordinier and Shil performed the first operation for diverticula in 1906 [1, 2].
Jejunoileal diverticula (excluding Meckel's diverticulum) are pseudodiverticula, resulting from a mucosal and submucosal herniation through the muscular layer of the bowels' wall in places of minor resistance to the intraluminal pressure such as the anatomic points where blood vessels penetrate the intestinal wall . The etiology is unclear. Krishnamurthy et al.  focused on abnormalities of the smooth muscles or of the myenteric plexus in order to explain intestinal dyskinesia. Kongara et al.  performed manometric studies of the small bowel and described functional abnormalities in patient with small bowel diverticula. These facts support the hypothesis that irregular intestinal contractions generate increased segmental intraluminal pressure, favoring the diverticula formation through the weakest point of the bowel. A connection between intestinal diverticulosis and rare neuromuscular disorders such as Cronkhite-Canada syndrome , Fabry's disease  and mitochondrial neurogastrointestinal encephalomyopathy  has been described. Diffuse gastrointestinal giant diverticulosis with perforation and malabsorpion associated with giant jejunal diverticula in Elhers-Danlos syndrome have also been reported [8, 9]. Progressive systemic sclerosis often involves the gastrointestinal tract and constitutes a characteristic example of proven dysmotility and acquired origin of the jejunoileal diverticulosis. Manometric studies, performed in patients with the disease, demonstrated intestinal dysmotility in 88% of the cases examined . Weston et al.  reported an important incidence of small bowel dilation and diverticula (42%) in patients with progressive systemic sclerosis. A case of association between jejunal diverticulosis and myasthenia gravis has recently published in order to emphasize the possible correlation between anticholinesterase drugs and increased intraluminal pressure . Primary or secondary amyloidosis is commonly associated with dysmotility disorders of the large and small bowel and cases of diverticular disease have been described [13–15]. Despite small bowel diverticulosis seems to be acquired, two cases of familiar predisposition have been reported [16, 17].
The incidence of jejunoileal diverticula in studies of the small bowel by enteroclysis is 2-2.3% which is comparable to autopsy data presenting an incidence of 1.3-4.6% for diverticula of the jejunum and ileum [18–20]. The jejunoileal diverticulosis is usually multiple, more frequently located in the jejunum and in the terminal ileum and probably due to the larger size of the vasa recta at these areas . Eighty percent of diverticula occur in the jejunum, fifteen percent in the ileum and five percent in both . Isolated jejunal diverticulosis coexists with diverticula of the esophagous (2%), of the duonenum (26%) and of the colon (35%) . The prevalence increases with the age and the disease presents a peak incidence at the sixth and seventh decades with a male predominance . The size of small bowel diverticula varies. Diverticula may measure from few millimeters up to more than 3 cm. Performing a web search of the relative literature for giant jejunal diverticula and using terms such as 'giant jejunal divericula', 'giant jejunal diverticulosis' and 'giant jejunoileal diverticulosis', we found a limited number of cases defined from the author's description as giant; one case associated with Ehlers-Danlos Syndrome and malabsorption , one associated with iron deficiency , two cases with diverticultis [24, 25], one presented with intestinal obstruction  and one manifested with intestinal bleeding [title only] . The problem in our research was the fact that in many case reports as well as in larger series, there was no objective measurement of the size of the diverticulum (intraoperative or pathological). In many reports, the description of the diverticula was based on no medical terms (egg, golf ball etc) or it was not reported at all [28, 29]. Liu et al.  in a series of 27 patients reported jejunoileal diverticula greater than 3 cm in 12 cases not specifying the precise size of the reported diverticula. Despite this problem, we identified a giant divericula measuring about 26 cm in a young patient with peritonitis [abstract only] .
The disease is usually silent. Nevertheless, Rodrigez et al.  reviewed the literature and noted symptoms in 29% of the cases. Many symptoms may be misdiagnosed as dyspepsia or irritable small bowel. Edwards described a symptom triad observed in these patients as 'flattulent dyspepsia' (epigastric pain, abdominal discomfort, flatulence one or two hours after meals) . Vague and chronic, mainly post prandial, epigastric cramping pain, bloating or abdominal fullness is usually referred. Anemia due to iron deficiency and megaloblastic anemia have often been reported and commonly attributed to malabsorpion, steatorreia, and vitaminic deficit [23, 33]. Malabsorpion could be justified by the non syncronous peristaltic movement of the bowel, the dilation of the diverticula, the stasis of the intestinal content and the bacterial overgrowth [1, 34–36].
Complications such as obstruction, hemorrhage, diverticulitis and perforation occur in 10%-30% of the patients [34, 35]. Some patient responds to the temporary interruption of the enteral nutrition, to a gastrointestinal relief with a nasogastric tube and to the administration of empirical, wide-spectrum antibiotics, however, complications requiring surgical intervention occur in 8-30% of patients [37, 38].
Incidence of diverticulitis with or without perforation ranges from 2% to 6% . Jejunoileal diverticulitis presented a high mortality rate in the past (24%), however, the mortality has been minimized because of the amelioration of the diagnostic, pharmaceutical and surgical protocols [40, 41]. Perforation causes localized or diffuse peritonitis but symptoms are non specific to justify differential diagnosis, considering that other abdominal conditions present similar clinical aspects. Complications such as abdominal abscesses, fistulas and hepatic abscesses are possible . Two authors described also 'microperforations' of the diverticula causing chronic, repetitive and asymptomatic pneumoperitoneum [42, 43]. Diverticulitis is not always the cause of a perforation. Foreign bodies as well as abdominal trauma may also cause perforation of jejunal diverticula [44, 45].
Mechanical obstruction can be caused by adhesions or stenosis due to diverticulitis, intussusception at the site of the diverticulum and volvulus of the segment containing the diverticula. In addition, sizable stones enclosed in the diverticula may apply pressure to the adjacent bowel wall or may escape from the diverticulum causing intestinal occlusion. Pseudo-obstruction, reported in 10-25% of cases, is usually associated with jejunal diverticulosis as a result of peritonitis (following diverticulitis), perforation, strangulation and incarceration of an enterolith within a diverticulum or related to the bacterial overgrowth and the visceral myopathy or neuropathy . A wide, overloaded with liquid diverticulum may function as a pivot causing volvulus [40, 45]. The formation of the enterolith may be de novo or around fruit seeds and vegetable material. The stone originates from biliar salts that deconiugated from the bacterial overgrowth within the diverticulum precipitate because of the more acidic pH of the jejunum .
Bleeding is a consequence of acute diverticulitis and due to the erosive results of the inflammation. Mucosal ulcerations compromise mesenteric vessels causing hemorrhage. Rodriguez et al., in a large series of 141 symptomatic cases, estimated bleeding in 2% .
Suspicion of jejunal diverticulosis is difficult and often the diagnosis is missed or delayed. Considering that jejunal diverticulusis is asymptomatic for a long time in most of the cases, diagnosis is usually made when the disease becomes symptomatic or complicated. Simple radiographs are not suggestive to make the diagnosis despite the fact that Nobles et al.  described a characteristic triad of clinical and radiographic findings of jejunoileal diverticulosis (abdominal pain, anemia and segmental dilatation in the epigastrium or in the left upper abdomen). In cases of complicated jejunal diverticulosis, plain abdominal X-ray series demonstrate distension of small bowel, air-fluid levels and pneumoperitoneum. Barium follow-through study and enteroclysis are more specific although their utility is limited in emergency conditions . Computed tomography may show focal areas of out-pouching of the mesenteric side of the bowel, localized intestinal wall thickening due to inflammation or edema, abscesses, free abdominal fluids and pneumoperitoneum. Multi slice CT seems to be promising in diagnosing jejunoileal diverticula and appears more specific than enteroclysis concerning small bowel diseases . Endoscopy does not identify diverticula but excludes other causes of obstruction or hemorrhage.
In cases of bleeding, a diagnostic and therapeutic approach with Tc99 RBC and mesenteric angiography seems do be specific . Upper GI endoscopy can identify diverticula to the second portion of the duodenum while double-ballon enteroscopy appear helpful in diagnosing small bowel disorders, however, emergency conditions such as obstruction or diverticulitis are significant limitations . Recently, a successful double-balloon enteroscopy treatment for bleeding due to jejunal diverticulosis has been reported . Wireless capsule endoscopy is a new hopeful technique for the detection of small bowel diseases, predominantly used in cases of occult intestinal bleeding. Although the presence of large diverticula is a relative contraindication to capsule endoscopy because of the possibility of the capsule's entrapment in small bowel diverticula, the application of this method in patients with isolated small bowel diverticulosis and occult intestinal bleeding should be decided with a relative prudence . Laparoscopy becomes a valid diagnostic approach for complicated cases, it is rapidly convertible in laparatomy and it can function as a guide in order to avoid usefulness laparotomies. In addition, laparoscopy, précising the area of the intestinal complication, guide the surgeon to the ideal incision site on the abdominal wall, minimizing the time of the operation, the post-operative pain and the morbidity due to a larger abdominal incision . A total laparoscopic treatment of sizable jejunal diverticulum has been recently reported .
Asymptomatic jejunoileal diverticulosis does not require intestinal resection . Some authors consider that patients with chronic symptoms can be treated conservatively and when symptoms are persistent or refractory to treatment, resection is imperative . Others, based on data demonstrating that jejunoileal diverticula, compared to diverticula of the duodenum, potentially will perforate and develop abscesses, recommend a more aggressive surgical approach in view of the lower post-operative risk of an elective intestinal resection [37, 55]. Exploratory laparotomy and resection of affected intestinal segment with primary anastomosis is mandatory in case of perforation, abscesses and obstruction. Although, Novac et al  presented a case series of perforated diverticulitis treated conservatively with antibiotic administration and CT-guided drainage of abdominal abscesses. The extent of the segmental resection depends on the length of the bowel affected by diverticula. If diverticula involve a long intestinal segment, as commonly happens, the resection should be limited to the perforated or inflamed intestinal segment in order to avoid a short bowel syndrome. Other surgical approaches such as the invagination of the diverticula, the primary closure of the perforation and omental patch and the diverticulectomy should be avoided since they present high mortality rates [40, 57]. One should also keep in mind that diverticula may recur in a patient undergone a segmental intestinal resection for diverticulosis since the mechanism of diverticula formation (neuropathy, myopathy etc.) still remains. Regarding enteroliths, some authors propose a manual or instrumental fragmentation of the stone and a gradual pushing of their fragments to the colon. Enterotomy or segmental resection should be reserved for complicated cases [26, 46].
In the case reported in this paper, the patient had a chronic abdominal discomfort or pain, however, he never visited the physician. The intestinal obstruction was the main symptom of presentation and obviously due to multiple overloaded jejunal diverticula and to pseudo-obstruction caused by the diverticulitis. The initial treatment with nasogastric tube and broad-spectrum antibiotics helped to limit inflammation and to avoid the extension of the diverticulitis, allowing us to perform an elective intestinal resection nine days after the initial admission. Anemia and hypoaluminemia were probably due to malabsorpion. CT scan demonstrated diverticula and excluded perforation. The enteroclysis confirmed the diagnosis.
Jejunal diverticulosis is more common than reported, affects usually older patients and must be considered in the differential diagnosis in patients with acute or chronic abdominal symptoms. A high degree of suspicion is necessary in view of the high mortality and morbidity rates resulting from a delayed diagnosis of the disease. The treatment of choice is surgical excision of the affected jejunal segment.
Written informed consent was obtained from the patient for publication of his medical data.
- Longo WE, Vernava AM: Clinical implications of jejunoileal diverticular disease. Dis Colon Rectum. 1992, 35: 381-388.View ArticlePubMed
- Williams R, Davidson DD, Serota AL, Wilson SE: Surgical problems of diverticula of the small bowel. Surg Gynecol Obstet. 1981, 152: 621-6.PubMed
- Krishnamurthy S, Kelly MM, Rohrmann CA, Schuffler MD: Jejunal diverticulosis. A heterogeneous disorder caused by a variety of abnormalities of smooth muscle or myenteric plexus. Gastrenterol. 1983, 85: 538-547.
- Kongara KR, Soffer EE: Intestinal motility in small bowel diverticulosis: a case report and review of the literature. J Clin Gastroenterol. 2000, 30: 84-6.View ArticlePubMed
- Cunliffe WJ, Anderson J: Case of Cronkhite-Canada syndrome with associated jejunal diverticulosis. Br Med J. 1967, 4: 601-2.PubMed CentralView ArticlePubMed
- Friedman LS, Kirkham SE, Thistlethwaite JR, Platika D, Kolodny EH, Schuffler MD: Jejunal diverticulosis with perforation as a complication of Fabry's disease. Gastroenterology. 1984, 86: 558-63.PubMed
- Aksoy F, Demirel G, Bilgiç T, Güngör IG, Ozçelic A: A previously diagnosed mitochondrial neurogastrointestinal encephalomyopathy patient presenting with perforated ileal diverticulitis. Turk J Gastroenterol. 2005, 16: 228-31.PubMed
- McLean AM, Paul RE Jr, Kritzman J, Farthing MJ: Malabsorption in Marfan (Ehlers-Danlos) syndrome. J Clin Gastroenterol. 1985, 7: 304-8.View ArticlePubMed
- Shapira O, Mavor E, Simon D, Rothstein H, Pfeffermann R: Multiple giant gastrointestinal diverticula complicated by perforated jejunoileal diverticulitis in Marfan Syndrome. Dig Surg. 1992, 9: 58-60.View Article
- Marie I, Levesque H, Ducrotté P, Denis P, Benichou J, Hellot MF, Cailleux N, Le Loët X, Joly P, Lauret P, Courtois H: Manometry of the upper intestinal tract in patients with systemic sclerosis: a prospective study. Arthritis Rheum. 1998, 41: 1874-83.View ArticlePubMed
- Weston S, Thumshirn M, Wiste J, Camilleri M: Clinical and upper gastrointestinal motility features in systemic sclerosis and related disorders. Am J Gastroenterol. 1998, 93: 1085-9.View ArticlePubMed
- Zuber-Jerger I, Endlicher E, Kullmann F: Bleeding jejunal diverticulosis in a patient with myasthenia gravis. Diagn Ther Endosc. 2008, 2008: 156496.PubMed CentralView ArticlePubMed
- Ng SB, Busmanis IA: Rare presentation of intestinal amyloidosis with acute intestinal pseudo-obstruction and perforation. J Clin Pathol. 2002, 55: 876.PubMed CentralView ArticlePubMed
- Patel SA, al-Haddadin D, Schopp J, Cantave I, Duarte B, Watkins JL: Gastrointestinal manifestations of amyloidosis: a case of diverticular perforation. Am J Gastroenterol. 1993, 88: 578-82.PubMed
- Díaz Candamio MJ, Pombo F, Yebra MT: Amyloidosis presenting as a perforated giant colonic diverticulum. Eur Radiol. 1999, 9: 715-8.View ArticlePubMed
- Koch AD, Schoon EJ: Extensive jejunal diverticulosis in a family, a matter of inheritance?. Neth J Med. 2007, 65: 154-155.PubMed
- Andersen LP, Schjoldager B, Halver B: Jejunal diverticulosis in a family. Scand J Gastroenterol. 1988, 23: 672-4.View ArticlePubMed
- Maglinte DD, Chernish SM, De Weese R, Kelvin FM, Brunelle RL: Acquired jejunoileal diverticular disease. A subject review. Radiology. 1986, 158: 577-580.View ArticlePubMed
- Salomonowitz E, Wittich G, Hajek P, Jantsch H, Czembirek H: Detection of intestinal diverticula by double-contrast small bowel enema: differentiation from other intestinal diverticula. Gastrointest Radiol. 1983, 8: 271-278.View ArticlePubMed
- Ross CB, Richards WO, Sharp KW, Bertram PD, Schaper PW: Diverticular diseases of the jejunum and its complications. Am Surg. 1990, 56: 319-324.PubMed
- Rodriguez HE, Ziaudin MF, Quiros ED, Brown AM, Podbielski FS: Jejunal diverticulosis and gastrointestinal bleeding. J C Gastrenterol. 2001, 33: 412-4.View Article
- Lempinen M, Salmela K, Kemppainen E: Jejunal diverticulosis: a potentially dangerous entity. Scand J Gastroenterol. 2004, 39: 905-9.View ArticlePubMed
- Shimayama T, Ono J, Katsuki T: Iron deficiency caused by a giant jejunal diverticulum. Jpn J Surg. 1984, 14: 146-9.View ArticlePubMed
- Pusztaszeria M, Christodoulou M, Proiettic S, Seelentaga W: Kayexalate intake (in sorbitol)and jejunal diverticulitis, a causative role or an innocent bystander?. Case Rep Gastroenterol. 2007, 1: 144-151.View Article
- Staszewicz W, Christodoulou M, Proietti S, Demartines N: Acute ulcerative jejunal diverticulitis: Case report of an uncommon entity. World J Gastroenterol. 2008, 14: 6265-6267.PubMed CentralView ArticlePubMed
- Balducci G, Dente M, Cosenza G, Mercantini P, Salvi PF: Multiple giant diverticula of the foregut causing upper gastrointestinal obstruction. World J Gastrenterol. 2008, 14: 3259-3261.View Article
- Callaghan J: Giant jejunal diverticulosis: a rare cause of massive upper gastro-intestinal hemorrhage. J Iowa Med Soc. 1971, 61: 152-5.PubMed
- Naude PJ, Nel LJ: Acquired diverticulosis of the small bowel. S Afr Med J. 1965, 39: 43-5.PubMed
- Fischer MH: False diverticula of the intestine. J Exp Med. 1901, 5: 333-52.PubMed CentralView ArticlePubMed
- Liu CY, Chang WH, Lin Sc, Chu CH, Wang TE, Shih SC: Analysis of clinical manifestations of symptomatic acquired jejunoileal disease. World J Gastrenterol. 2005, 11: 5557-5560.View Article
- Takehito E, Tsuyoshi K, Ichiro H: A case of large diverticulum of the distal jejunum. J Jap Surg Assoc. 2004, 65: 1850-1854.View Article
- Edwards HC: Diverticula of the Small Intestine. B J of Radiology. 1949, 22: 437-442.View Article
- Drude RB Jr, Finkelman D, Davis WD, Ferrante WA: Malabsorption in jejunal diverticulosis treated with resection of the diverticula. Dig Dis Sci. 1980, 25: 802-6.View ArticlePubMed
- Akhrass R, Yaffe MB, Fischer C, Ponsky J, Shuck JM: Small-bowel diverticulosis: Perceptions and reality. J Am Coll Surg. 1997, 184: 383-8.PubMed
- Wilcox RD, Shatney CH: Surgical implications of jejunal diverticula. South Med J. 1988, 81: 1386-1391.View ArticlePubMed
- Singh VV, Toskes PP: Small bowel bacterial overgrowth: Presentation, Diagnosis and treatment. Curr Gastrenterol Rep. 2003, 5: 365-372.View Article
- Wilcox RD, Shatney CH: Surgical significance of acquired ileal diverticulosis. Am Surg. 1990, 56: 222-225.PubMed
- Rockey DC: Occult gastrointestinal bleeding. Current Diagnosis & Treatment in Gastrenterology. Edited by: Friedman SL, McQuiad KR, Grendell JH. 2003, McGraw-Hill, 83-95.
- Sibille A, Willocx R: Jejunal diverticulitis. Am J Gastrenerol. 1992, 87: 655-658.
- de Bree E, Grammatikakis J, Christodoulakis M, Tsiftsis D: The clinical significance of acquired jejunoileal diverticula. Am J Gastrenterol. 1998, 93: 2523-28.View Article
- Tsiotos GG, Farnel MI, Ilstup DM: Non Meckelian jejunal or ileal diverticulosis:an analysis of 112 cases. Surgery. 1994, 116: 726-732.PubMed
- Alvarez J Jr, Dolph J, Sheccey J, Marjani M: Recurrent rupture of jejunal diverticula. Conn Med. 1982, 46: 373-378.
- Franzen D, Gürcler T, Meczger U: Multiply recurrent perforated jejunal diverticulitis. Chirurgia. 2002, 72: 1218-1220.View Article
- Eckhauser FE, Zelenock GB, Freier DT: Acute complications of jejuno-ileal pseudodiverticulosis: Surgical implications and management. Am J Surg. 1979, 138: 320-323.View ArticlePubMed
- Chou CK, Mak CW, Hou CC, Chang JM: CT of large small bowel diverticulum. Abd Imaging. 1998, 23: 132-4.View Article
- Chugay P, Choi J, Dong XD: Jejunal diverticular disease complicated by enteroliths: report of two different presentations. World J Gastrointest Surg. 2010, 2: 26-29.PubMed CentralView ArticlePubMed
- Nobles E: Jejunal diverticula. Arch Surg. 1973, 102: 372-374.
- Benya EC, Ghahremani GC, Brosnan JJ: Diverticulitis of the jejunum. Clinical and radiological features. Gastrointest Radiol. 1991, 16: 24-28.View ArticlePubMed
- Bitterling H, Rock C, Reiser M: Computed tomography in the diagnosis of inflammatory bowel disease-methodology of MSCT and clinical results. Radiologe. 2003, 43: 17-25.View ArticlePubMed
- Yen HH, Chen YY: Jejunum diverticulosis: a limiting condition to double ballon enteroscopy. Gastrointest Endosc. 2006, 64: 847.View ArticlePubMed
- Yang CW, Chen YY, Yen HH, Soon MS: Successful double balloon enteroscopy treatment for bleeding jejunal diverticulum: A case report and review of the literature. J Laparoendos Adv Surg Techn. 2009, 9: 637-640.View Article
- Gaba RC, Schlesinger PK, Wilbur AC: Endoscopic video capsules: Radiologic findings of spontaneous entrapment in small intestinal diverticula. AJR. 2005, 185: 1048-1050.View ArticlePubMed
- Cross MJ, Snyder SK: Laparoscopic-directed small bowel resection for jejunal diverticulitis with perforation. J Laparoendosc Surg. 1993, 3: 47-49.View ArticlePubMed
- Cang N, Khullar R, Sharma A, Soni V, Baijal M, Chowbey P: Total laparoscopic management of large complicated jejunal diverticulum. J Minim Access Surg. 2009, 5: 115-7.View Article
- Chendrasekhar A, Timberlake GA: Perforated jejunal diverticula: an analysis of reported cases. Am Surg. 1995, 61: 984-988.PubMed
- Novac JS, Tobias J, Barkin JS: Non surgical management of acute jejunal diverticulitis: A review. Am J Gastrenterol. 1997, 92: 1929-1931.
- Englund R, Jensen M: Acquired diverticulosis of the small intestine: case reports and literature review. Aust N Z J Surg. 1986, 56: 51-54.View ArticlePubMed
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