British Journal of Radiology 74 (2001),1142-1144 © 2001 The British Institute of Radiology
Stromal tumour within a Meckel's diverticulum: CT and ultrasound findings
A T Johnston, BSc, MRCS
1
A L Khan, FRCS
1
R Bleakney, M.Rad., FRCR
2 and
R A Keenan, ChM, FRCS
1
Departments of 1Surgery and 2Radiology, Aberdeen Royal Infirmary, Foresterhill Road, Aberdeen AB25 2ZN, UK
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Abstract
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The incidence of tumours within a Meckel's diverticulum is 0.5–3.2%. Their pre-operative diagnosis is rare. We report a case of an incidentally found gastrointestinal stromal tumour within a Meckel's diverticulum in a patient presenting with acute appendicitis. The tumour was demonstrated pre-operatively by ultrasound and CT.
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Case report
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A 58-year-old male presented with a 20 hour history of right iliac fossa (RIF) pain. On clinical examination the patient was apyrexial and had guarding in the RIF with rebound tenderness. Digital rectal examination demonstrated a smooth, firm mass on the right side. The patient's white cell count was elevated to 14.9 x 109 l-1 (normal range 4.0–10.0 x 109 l-1). Ultrasound examination of the abdomen and pelvis was undertaken because of the findings on rectal examination (Figure 1
). This showed a slightly thickened viscus in the RIF, consistent with appendicitis. The examination also demonstrated a solid, hypoechoic, rounded mass lying anterior to the bifurcation of the aorta and indenting the dome of the bladder. The mass had an echobright posterior wall consistent with calcification.
CT was performed using 10 mm axial slices following iv contrast medium. The mass was again identified, appearing spherical and well circumscribed. It measured 6 x 6 cm2 and was of homogeneous soft tissue density with a partially calcified wall. The mass was immediately adjacent to loops of small bowel in the mesentery (Figure 2) and to the bladder (Figure 3). There was no retroperitoneal lymphadenopathy and the fat planes around the mass were clear, with no evidence of desmoid reaction. The mass was thought to represent either a complicated mesenteric cyst or a soft tissue sarcoma arising in the mesentery.
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Figure 2. CT of the pelvis showing the pelvic mass (arrow) immediately adjacent to loops of bowel in the mesentery.
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Laparotomy showed that the mass was a calcified Meckel's diverticulum. 10 cm of small bowel containing the Meckel's mass was excised and an end-to-end anastamosis was performed. The diagnosis of appendicitis was confirmed and appendectomy was performed. Histological sections of the Meckel's diverticulum showed the presence of a circumscribed, solid, spindle cell tumour. The features were those of a gastrointestinal stromal tumour (GIST).
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Discussion
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Meckel's diverticulum, a remnant of the omphalomesenteric duct, is present in 1–3% of the population. Tumours within a Meckel's diverticulum are uncommon but well recognized, with a reported incidence of 0.5–3.2% [1–4]. GISTs comprise a significant proportion of these tumours [1].
GISTs comprise the large majority of mesenchymal tumours of the gastrointestinal tract that cannot be verified either as neurogenic or of smooth muscle origin. The term GIST has also been used to include all mesenchymal tumours, including leiomyomas and schwannomas [5].
Prognosis of metastatic GIST is poor [1]. When the tumour is localized, prognosis is more difficult to ascertain. The main features of GIST associated with clinically aggressive behaviour include a tumour size of 5 cm or more and a high mitotic count [6]. Other factors giving a poor prognosis include high cellularity, tumour necrosis, a solid pattern of growth and activating mutations in the c-kit gene [5, 7].
There is no consensus on the management of an uncomplicated Meckel's diverticulum found during surgery. Although resection prevents future complications, the associated risks may outweigh any potential benefit [1, 3, 8, 9]. However, formal resection is appropriate if a Meckel's mass is found.
Radiological appearances of GIST may include asymmetrical thickening of the bowel wall initially, but more commonly an exophytic soft tissue mass with relatively well defined margins is seen [10]. Areas of necrosis are present in up to 70% of tumours [11] and particularly in larger tumours that frequently undergo central necrosis, due to rapid growth, and subsequent ischaemia [10]. These also demonstrate heterogeneous contrast enhancement [10]. Areas of calcification and haemorrhage are seen within 7% and 64% of tumours, respectively [11].
Most tumours in Meckel's diverticulum are found incidentally intraoperatively [4, 12]. CT is of limited use in diagnosis owing to difficulty in distinguishing a diverticulum from intestinal loops [13, 14]. However, as in this case, CT may demonstrate a Meckel's diverticulum complicated by tumour or inflammation. Less commonly, calcification specifically related to a Meckel's diverticulum may be seen in the form of either enteroliths [15] or as milk of calcium [16]. Both are thought to be caused by stasis of intestinal contents. The diagnosis of Meckel's diverticulum may also be suspected if attachment of the diverticulum to the umbilicus is seen [14]. Although rare, a Meckel's diverticulum tumour should be considered when CT or ultrasound demonstrate a pelvic mass closely associated to small bowel loops.
Received for publication August 17, 2000.
Revision received August 2, 2001.
Accepted for publication August 14, 2001.
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References
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