DOI:10.2214/AJR.06.0462
AJR 2006; 187:W438
© American Roentgen Ray Society
An Extreme Case of Retrorenal Colon
Ryan Chan and
David K. B. Li
University of Ottawa Ottawa, ON, Canada
University of British Columbia Hospital Vancouver, BC,
Canada
WEB—This is a Web exclusive article.
An 84-year-old woman with a remote history of cholecystectomy was referred
for investigation of intermittent right lower quadrant fullness and
discomfort. Abdominal CT performed with the patient supine with positive oral
and IV contrast material revealed extreme posterior and retrorenal positioning
of the ascending and descending colon, wrapping around the lower pole of the
kidneys and extending almost to the posterolateral border of the psoas muscles
(Figs. 1A,
1B, and
1C).
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Fig. 1A —84-year-old woman with retrorenal colon. Axial enhanced CT
images show colon wrapping around lower pole of kidneys and extending
posteromedially to psoas muscles (C). Note paucity of fat in
perinephric space.
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Fig. 1B —84-year-old woman with retrorenal colon. Axial enhanced CT
images show colon wrapping around lower pole of kidneys and extending
posteromedially to psoas muscles (C). Note paucity of fat in
perinephric space.
|
|
View larger version (105K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —84-year-old woman with retrorenal colon. Axial enhanced CT
images show colon wrapping around lower pole of kidneys and extending
posteromedially to psoas muscles (C). Note paucity of fat in
perinephric space.
|
|
Retrorenal positioning of the colon, as determined by a line drawn
coronally through the posterior margin of the kidney, has been reported
variably in 1-14% of the population
[1,
2]. Normally, the ascending and
descending colon lie anterior to the kidneys in the anterior pararenal space,
which is bordered anteriorly by the posterior parietal peritoneum, posteriorly
by the anterior renal (Gerota's) fascia, and posterolaterally by the
lateroconal fascia (formed by the fusion of the anterior and posterior renal
fascia at their lateral borders). Two theories have been proposed for the
normal variant of the retrorenal colon. The first theory is that the more
lateral and posterior colonic positioning is a result of a smaller amount of
perinephric fat [3]. The second
is that the absence of the lateroconal fascia, or its formation more
posteromedially, may allow the colon to extend around the posterior margin of
the perirenal space [1].
The retrorenal position of the colon places the colon at risk for
iatrogenic trauma during percutaneous procedures directed at the kidneys such
as biopsy, percutaneous nephrostomy, and nephrolithotomy. The frequency of
retrorenal colon was found to be five times higher when patients were
positioned prone (the favored position for percutaneous procedures) rather
than supine [4]. It has been
suggested that the prone positioning results in a more gas-distended colon,
which might more easily displace the renal fascia and possibly even dissect
between the laminae of the posterior renal fascia.
References
- Sherman JL, Hopper KD, Green AJ, Johns TT. The retrorenal colon on
computed tomography: a normal variant. J Comput Assist
Tomogr 1985; 9:339
-341[Medline]
- Prassopoulos P, Gourtsoyiannis N, Cavouras D, et al. A study of the
variation of colonic positioning in the pararenal space as shown by computed
tomography. Eur J Radiol 1990;10
: 44-47[CrossRef][Medline]
- Hadar H, Gadoth N. Positional relations of colon and kidney
determined by perirenal fat. AJR 1984;143
: 773-776[Abstract/Free Full Text]
- Hopper K, Sherman J, Luethke J, et al. The retrorenal colon in the
supine and prone patient. Radiology 1987;162
: 443-446[Abstract/Free Full Text]
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