CT Diagnoses of Rare Causes of Acute Left Lower Abdominal Pain, a Pictorial Essay Poster No.:

R-0054

Congress:

2015 ASM

Type:

Educational Exhibit

Authors:

M. George, A. Thomas, R. Dutta, K. Gummalla; Singapore/SG

Keywords:

Education, CT, Abdomen, Acute

DOI:

10.1594/ranzcr2015/R-0054

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Learning objectives -Describe the role of multidetector CT in diagnosing rare causes of acute left lower abdominal pain. -Recognize CT findings of rare causes of left lower abdominal pain. -Discuss the differential diagnosis

Background Introduction

•Left lower abdominal pain is often encountered in patients presenting to the emergency department. With a vast list of differential diagnoses, most are benign conditions which are treated conservatively while a smaller percentage of cases may include potentially life-threatening conditions that may require emergency surgery. •Multidetector CT is an important noninvasive method for evaluation of patients with acute abdominal pain, as history and physical examination results are not specific and especially since plain radiograph are often non contributory. •Some of the differentials for acute left lower abdominal pain include the following, diverticulitis, renal colic, ischeamic colitis, inflammatory bowel disease, tubo-ovarian pathology and malignancy. •More rare causes include left sided appendicitis, obturator hernia causing obstruction, epiploic appendagitis, foreign body bowel perforation, tumour perforation of sigmoid colon, sigmoid volvulus, ovarian torsion, ovarian cyst rupture, etc.

Imaging findings OR Procedure details

1)Epiploic appendagitis

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A rare self limiting inflammatory/ischaemic process involving the appendix epiploica of the large bowel (a fat-density ovoid structure adjacent to colon). CT findings (Fig 1) •thin high-density rim (1-3mm thick) •surrounding inflammatory fat stranding •central hyperdense dot - thrombosed vascular pedicle •Chronically, an infarcted appendix epiploica may calcify, and may detach to form an intraperitoneal loose body.

2)Left sided appendicits It develops in association situs inversus totalis or midgut malrotation CT findings (Fig 2,3) •dilated appendix with distended lumen in the left side of abdomen. •thickened and enhancing wall •periappendiceal inflammation, including stranding of the adjacent fat and thickening of the lateral conal fascia or mesoappendix. •extraluminal fluid. •Appendicolith may also be identified.

3)Obturator hernia An obturator hernia is a rare type of abdominal hernia, and can be clinically very difficult to diagnose. The hernia lie superficial to obturator externis and deep and inferior to pectineus muscle. CT findings (Fig 4,5) •Either fluid or bowel in the medial upper thigh.

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•Signs of complication including: bowel obstruction and perforation secondary to strangulation

4)Tumour perforation It occurs due to tumour ischaemia or necrosis. Typically seen in the sigmoid. CT findings (Fig 6) •Bowel mass at the site of perforation. •Perilesional inflammation •Extraluminal fluid and air •Inflammatory phlegmon •Abscess formation

5)Bowel perforation due to foreign body It occurs following inadvertent ingestion of sharp foreign bodies. Culprits include animal bones, fish bones, toothpicks, etc. CT findings (Fig 7) •Free fluid or abscess. Site of perforation may be seen. •The object may be seen piercing the bowel wall, with associated inflammatory change

6)Sigmoid volvulus Cause of large bowel obstruction and occurs when the sigmoid colon twists on the sigmoid mesocolon. CT findings (Fig 8) •Large gas-filled loop without haustral markings, forming a closed loop obstruction. •Twisting of the mesentery and mesenteric vessels -whirls sign.

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7)Gallstone ileus An uncommon cause of a mechanical small bowel obstruction and occurs when a gallstone passes into the small bowel and impacts. CT findings (Fig 9,10) •Gallstone in the small bowel. •bulging of the bowel just prior to the transition point. •Site of fistulization is often visible.

8)Diverticular abscess Complication of diverticulitis CT findings (Fig 11) •Rounded collection of fluid adjacent to sigmoid which contains many diverteculae and is thick walled.

9)Ovarian torsion Rotation of the ovary and portion of the fallopian tube on the supplying vascular pedicle CT findings (Fig 12) •Twisted ovarian pedicle is pathognomonic. •Enlarged ovary. •Distended pedicle. •lack of enhancement may be seen •surrounding fat stranding oedema and free fluid

10)Ruptured ovarian cyst

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One of the most common causes of acute pelvic pain in premenopausal women. These are usually diagnosed on ultrasound. CT findings (Fig 13) •Thin wall cyst of varying size with distortion of the wall. •Haemoperitoneum.

Images for this section:

Fig. 1: Inflammatory fat stranding with thin high-density rim (arrow)

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Fig. 2: Dilated appendix (arrow) with appendicolith (star) in the left side of abdomen.

Fig. 3: Periappendiceal inflammation (arrow head) Page 7 of 15

Fig. 4: Bowel in the medial upper thigh (arrow) deep to pectineus

Fig. 5: Obturator hernia causing bowel obstruction (star).

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Fig. 6: Bowel mass at the site of perforation (star).Extraluminal fluid and air (arrow)

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Fig. 7: Site of perforation (arrow) in small bowel loop with adjacent abscess (star).

Fig. 8: Twisting of the mesentery and mesenteric vessels (arrow) with closed loop obstruction

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Fig. 9: Gallstone in the small bowel (star) with proximal bowel dilatation (arrow)

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Fig. 10: Site of fistulization (arrow head).

Fig. 11: Rounded collection of fluid (arrow) adjacent to sigmoid.

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Fig. 12: Twisted ovarian pedicle ( arrow) with an enlarged left ovary (star).

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Fig. 13: Thin wall cyst with distortion of the wall (arrow) and haemoperitoneum (star).

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Conclusion Multidetector CT has revolutionized the diagnosis of rare causes of abdominal pain with its high resolution, image quality and decreased scan time. Rare causes of abdominal pain which were once difficult to diagnose are increasingly being diagnosed by multidetector CT leading to decreased patient morbidity and mortality.

Personal information References 1)Rosen MP, Siewert B, Sands DZ. Value of abdominal CT in the emergency department for patients with abdominal pain. Eur Radiol2003; 13(2): 418-424. 2)Cubillo E. Obturator hernia diagnosed by computed tomography. AJR Am J Roentgenol. 1983:140 (4):735-6

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