A b d o m Imaging 20:315 - 3 1 6 (1995)

Abdominal

Ima ,ing

9 Springer-VerlagNew York Inc. 1995

CT diagnosis of intestinal ascariasis S. C. Hommeyer, 1'* G. S. Hamill, 1 J. A. Johnson 2 IDepartment of Radiology, University of Washington (SB-05), 1959 Pacific St. NE, SB-05, Seattle, W A 98195, U S A 2Department of Radiology, Harborview Medical Center (ZA-65), 325 9th Ave., Seattle, W A 98104, USA Received: 19 May 1994/Accepted: 14 June 1994

Abstract The clinical symptoms and appearance by computed tomography of intestinal ascariasis are described in a patient with unsuspected Ascaris lumbricoides infestation. Key words: Ascariasis--Ascaris Iumbricoides--Intestinal parasite, CT.

The radiological appearance of intestinal Ascaris lumbricoides infestation and associated complications have been described for plain radiography, barium examination, ultrasonography, and endoscopic retrograde cholangiopancreatography (ERCP) [1-5]. Although the utility of computed tomography (CT) in evaluating for intraabdominal pathology complicating parasitic infestation has been shown [1, 5, 6, 8], the CT appearance of intestinal ascarid infestation has not been described. We report a case of unsuspected ascariasis initially diagnosed during an abdominal CT examination.

Case Report A 41-year-old native Vietnamese female who had immigrated to the United States 4 months prior to presentation developed nausea, vomiting, and dull, intermittent midabdominal pain over 2 days. She was mildly febrile to 38.2~ (100.8W) at presentation but had a markedly elevated white blood cell count (WBC) of 30,000 with a left shift (93% neutrophils, no eosinophiles). Her bilirubin, liver function tests, and coagulation times were normal, and the remainder of her laboratory values were not contributory to the case. On the night of admission the patient's abdominal films demonstrated a nonspecific bowel gas pattern but showed progressive small bowel dilatation the following 2 days, which was more consistent with

* Present address: Department of Radiology, University of Minnesota, Box 292, 420 Delaware St. SE, Minneapolis, M N 55455, USA Correspondence to: S. C. Hommeyer

Fig. 1. CT appearance of A. lumbricoides. A Axial CT scans show ascarid worm coursing within the opacified small bowel (straight arrows). B Magnified view demonstrates contrast within gut of parasite (curved arrows).

partial small bowel obstruction than ileus. Because of her markedly elevated W B C and clinical concern of intraabdominal abscess, a CT study was obtained, which showed no evidence of abscess. However, the CT did show a long, thin, tubular soft-tissue structure coiled within the patient's small bowel, outlined by oral contrast (Fig. 1A). The appearance was consistent with that expected of an Ascaris worm. Closer evaluation revealed a thin column of oral contrast within the gut of the worm (Fig. 1B). The diagnosis was suggested to the clinical service and confirmed the following day when Ascaris eggs were identified in a smear of the patient's stool. The patient was treated with 100 mg of mebenazole for 3 days, as well as broad-spectrum antibi-

316 otics for 6 days. Although mild abdominal pain persisted, the patient's partial small bowel obstruction and leukocytosis resolved before she was discharged.

Discussion Ascaris lumbricoides infests the intestinal tract of approximately one-quarter of the world's population, mostly involving the peoples of developing countries [ 1, 7]. The clinical and radiological manifestations of ascariasis are variable because the organism travels through many human organ systems during its life cycle. Respiratory symptoms are often the first to appear and occur after the larvae penetrate the intestinal mucosa, traverse the portal and hepatic veins, and finally settle in the pulmonary alveoli [ 1]. Following a growth phase in the lung, the larvae migrate to the larynx and are swallowed, with larval maturation occurring in the small bowel and continued symptomatology related to the abdomen. Although many patients are symptom free during the intestinal phase of the disease, others incur a variety of symptoms including nausea, vague abdominal discomfort, colicky pain, diarrhea, or obstruction. Migration of the adult worms into the biliary or pancreatic ducts may result in jaundice, cholangitis, cholecystitis, pancreatitis, and abscess formation. Appendicitis and oriental cholangiohepatits have also been associated with A. lumbricoides infestation [1, 2, 8]. On standard barium examination the diagnosis of ascariasis is made by identifying the tubular-filling defect of the worm within the host's opacified small bowel lumen. The lumen of the worm's gut is also frequently barium filled, thereby confirming the diagnosis [1, 2]. Whereas the CT appearance of intestinal ascariasis has not been previously described, the findings are not surprising: a long tubular structure outlined by the contrait-filled small bowel, a trace amount of contrast

S.C. Hommeyer et al.: CT diagnosis of intestinal ascariasis

within the gut of the worm. Considering the tubular nature of the parasite, one must resist the temptation to dismiss hastily the finding as an enteric feeding tube or as artifact because, unlike a barium examination where the worm is seen in its entirety, with CT the worm will be seen only in small sections on multiple images. Giving added consideration to the diagnosis of worm infestation has become more important in Western countries with the increasing number of immigrants from endemic areas who are being treated in many of our urban medical centers. Though CT would not be considered the diagnostic method of choice by either parasitologists or infectious disease specialists, many of our clinical colleagues may quickly turn to CT to sort out a patient's vague abdominal complaints or a confusing clinical history given through a translator. Radiologists should remain alert to the possibility of unexpected or unusual diseases. References 1. Reeder M, Palmer P. Infections and infestations. In: Freeny PC, Stevenson GW, eds. Margulis and Burhenne's alimentary tract radiology. St. Louis: Mosby. 1994:926-930 2. Ekberg O, Jones B, Herlinger H. Infections and other inflammatory conditions. In: Gore RM, Levin MS, Lauffler I, eds. Textbook of gastrointestinal radiology. Philadelphia: WB Saunders. 1994:845846 3. Price J, Leung JW. Ultrasound diagnosis of ascariasis lumbricoides in the pancreatic duct: the "four-lines" sign. Br J Radiol 1988;61(725):411-413 4. Cerri GC, Leite GJ, Simoes JB, et al. Ultrasonographic evaluation of ascaris in the biliary tract. Radiology 1983;146:753-754 5. Sheikh Mohamed AR, Karawi MA, Yasawy MI. Modem techniques in the diagnosis and treatment of gastrointestinal and biliary parasites. Hepatogastroenterology 1991;38:180-188 6. Radin DR, Vachon LA. CT findings in biliary and pancreatic ascariasis. JCAT 1986;10:508-509 7. Walsh JA, Warren KS. Selective primary care: An interim strategy for disease control in developing countries. N Eng J Med 1979;301:967 8. Lim JH. Oriental cholangiohepatitis: Pathologic, clinical and radiologic features. A JR 1991;157:1-8