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Bowel wall thickening on ultrasound simulates appearance of kidney. The appearance of kidney on contrast enhanced computed tomography is entirely different. However, surprisingly bowel wall thickening or mass can mimic this appearance even on contrast enhanced computed tomography. A case of pyloric malignancy with pseudokidney appearance on contrast enhanced computed tomography is being reported. [J Indian Med Assoc 2007; 105: 88-9]
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Key words : Pseudokidney sign, contrast enhanced computed tomography, bowel wall thickening.
The terminology of ‘pseudokidney sign’ on computed tomography (CT) is the first of its kind to be described. Here
in this report, a 48 years old woman presented with pain abdomen and feeling of fullness after taking meals since last 2 months. Contrast enhanced CT (CECT) showed the thickening of the 3 layers of pylorus simulating that of a kidney, thus, named as ‘pseudokidney sign’.
Case Report
A 48 years old woman presented to surgery outpatients’ department with complaints of pain in abdomen, which increased on empty stomach, feeling of fullness after taking meals, anorexia and lassitude since two months.
Examination — Right supraclavicular lymphadenopathy was present. Per abdomen examination revealed fullness in epigastrium and succussion splash .
Investigations — Ultrasound abdomen showed thickening of the wall of pylorus. Posterior wall measured 1.5cm, which was suggestive of a growth in pylorus. Barium meal study showed narrowing in the region of pyloric canal with no obvious ulceration or growth. Endoscopy showed narrowing of pyloric canal and endoscopy guided biopsy was taken. Histopathology confirmed it as epithelial cell malignancy. CT abdomen was done for staging of carcinoma stomach. One and half hours prior to the procedure 700 ml of 2% of barium sulphate suspension (diluted in water) was given orally. Scanning was done in supine position and also in right lateral decubitus position. Prior to CT study, 200 ml of oral contrast was given immediately. Precontrast, 10mm, axial slices of upper abdomen were obtained. Postcontrast (100ml infusion at the rate of 0.3ml/second by power injector) 10mm; axial slices were obtained from the level of diaphragm to the pelvic inlet.
CT abdomen showed concentric thickening in the wall of pylorus on plain study and on postcontrast study three different layers could be identified consisting of : (A) Innermost layer of barium coating over.mucosa; (B) middle enhancing layer of mucosa; (C) outermost hypoattenuating layer of thickened muscle arranged concentrically. All these three layers on cross-sectional study were simulating appearance of kidney (Fig 1). On CECT abdomen, a ‘pseudokidney sign’ was attributed to that appearance of concentric pyloric wall thickening on postcontrast CT study of abdomen. There was no invasion of perigastric fat plane, no lymphadenopathy, no invasion of surrounding organs.
Discussion
CT is important diagnostic tool for evaluation of the cause of gastric wall thickening1,2. Several modifications in routine protocol have been suggested for better visualisation of gastric wall pathologies. Ninety per cent individuals have gastric wall thickness less than 1cm with adequate distension of stomach1. But, thick gastric walls were observed in many patients without gastric pathologies3. In a study conducted by Rockey et al4, endoscopy demonstrated abnormalities in majority of cases of bowel wall thickening. As also in the present case the CT diagnosis was initially confirmed by endoscopic biopsy. Modification with drug induced hypotonia and water filling for study of depth of tumour invasion was also done5.
‘Pseudokidney sign’ in ultrasound is an entity described by Lutz and Petzoldt6, given to a bowel mass showing: (1) Inner hyperechoic mucosa, (2) alternate layers of hypoechoic and hyperechoic muscularis mucosae and muscles.
This resembles the appearance of kidney on ultrasound, which looks like: (1) Inner hypoechoic medulla, and (2) outer hyperechoic cortex.
In IV CECT kidney will appear as: (1) Innermost zone of contrast in collecting system, (2) middle and outermost layers of enhancing corticomedullary parenchyma (lower in attenuation than that of contrast).
Whereas, in this case, bowel thickening in concentric fashion on oral and IV CECT is showing three distinct layers (Fig 1): (1) Inner zone of oral contrast covering mucosal aspect, (2) middle zone of enhancing mucosa, (3) outermost zone of hypoattenuated thickened concentric muscle layer; which is simulating appearance of kidney on IV CECT. Although ‘pseudokidney appearance’ of a bowel mass on ultrasonography is well recognised, to the best of our knowledge this appearance of pseudokidney on CECT has not been described earlier.
Reference
1 Balfe DM, Koehler RE, Karstaedt N, Stanley RJ, Sagel SS — Computed tomography of gastric neoplasms. Radiology 1981; 140: 431-6.
2 Scatarige JC, DiSantis DJ — CT of the stomach and duodenum. Radiol Clin North Am 1989; 27: 687-706.
3 Komaki S — Normal or benign gastric wall thickening demonstrated by computed tomography. J Comput Assist Tomogr 1984; 6: 1103-7.
4 Rockey DC, Halvorsen RA Jr, Higgins JL, Cello JP — Prospective evaluation of patients with bowel wall thickening. Am J Gastroenterol 1995; 90: 99-103.
5 Rossi M, Broglia L, Graziano P — Local invasion of gastric cancer: CT findings and pathological correlation using 5mm incremental scanning, hypotonia, and water filling. AJR Am J Roentgenol 1999; 72: 383-8.
6 Lutz H, Petzoldt R — Ultrasound patterns of space occupying lesions of the stomach and the intestine. Ultrasound Med Biol 1976; 2: 129-31.
Department of Radiology, Government Medical College, Nagpur 440003
*MBBS, MD, Associate Professor
**MBBS, Resident
***MBBS, MD, Professor and Head of the Department
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