ANOMALOUS INFERIOR VENA CAVA ASSOCIATED WITH HORSESHOE KIDNEYS THEODORE R. SMITH,
AND ANDRE1 FROST,
Two cases are presented in which anomalies of the inferior vena cava were associated with horseshoe kidneys. Radiological demonstration of such combined variation is rare, only one case of duplicated inferior vena cava with horseshoe kidney having been found in the literature. The embryological basis for these anomalies is reviewed. A possible explanation for their coexisting occurrence is also specula0 Elsevier Science Inc., 1996 tively raised.
abdominal pain. Incidentally found were horseshoe kidneys, and a duplication of the IVC (Figure 1). The IVC bifurcation was superior to the kidneys, and the duplicated venous system posterior to the renal isthmus. The left and right IVC did not communicate with each other and joined widely separated left and right iliac veins. There were no urinary symptoms.
A 61-year-old woman was clinically thought to have an enlarged left lobe of the liver. An abdominal CT scan revealed an asymptomatic horseshoe kidney and a right renal cyst. The IVC was noted to be anterior to the renal isthmus (Figure 2), while the aorta was in a normal position.
INTRODUCTION Anomalous inferior vena cava (IX) and horseshoe kidneys are relatively uncommon. While a variable arterial supply to horseshoe kidney is well known, anomalous IVC association is much less frequent and not generally appreciated. Recently we saw two such anomalies of the IVC in association with horseshoe kidneys, both of which were asymptomatic incidental findings.
CASE REPORT Case
An 8%year-old woman with a history of breast, ovarian and colon carcinomas, including partial colonic resection, had a computed tomography (CT) scan for From the Department of Radiology, Jack D. Weiler Hospital of the Albert Einstein College of Medicine, Bronx, New York. Address reprint requests to: Theodore R. Smith, MD, Department of Radiology, Jack D. Weiler Hospital of the Albert Einstein College of Medicine, 1825 Eastchester Road, Bronx, NY 10461. Received November 15, 1994; accepted January 20, 1995. CLINICAL IMAGING 1996;20:276-278 0 Elsevier Science Inc., 1996 655 Avenue of the Americas, New York, NY 10010
DISCUSSION The suprarenal portion of the IVC is normally mainly derived from the right subcardinal vein, and the infrarenal portion of the IVC from the right supracardinal vein. (By the fourth embryological week there are paired cardinal veins, the anterior cardinals draining the cephalic portion and posterior cardinals draining the remaining body. At 7 weeks, the subcardinal veins appear as a second set of paired symmetrical veins, ventral and medial to the paired cardinal veins. The subcardinals become dominant by the seventh week as the posterior cardinals involute for the most part (although the iliac veins are derived from them). A third series of paired veins, the supracardinal veins (also called dorsal venous lines), then develop dorsal and medial to the paired cardinal veins. Anastomoses exist between the three paired systems, including subcardinal to supracardinal veins. The i&arena1 IVC is normally derived from the right supracardinal vein. The
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FIGURE 1. Duplicated inferior vena cava (NC) with horseshoe kidney. (A) single IVC above the kidneys (arrow). (B) Bifurcation of the IVC into right and left (arrowheads) just above the isthmus level. (C) The left IVC (arrowhead) larger than the right IVC (arrowhead) posterior to the fused kidneys. (D) Slightly caudal section shows the right TVC larger than the left one (arrow&ends).
suprarenal or prerenal IVC is derived from the right subcardinal vein, which anastomoses inferiorly to the right supracardinal and superiorly with the posthepatic TVC (arising from the right vitelline vein).) A duplicated IVC may result from persistence of normally ablated left supracardinal veins joined together with the right-sided system (l-3). It has a prevalenc:e of 0.2 to 3.0% (1. 2, 4). Duplicated IVC usually have a venous communication at or near the common iliac level, but case 1 did not have any significant connection. Also, previous reports classified such duplications as being of equal size or left- or right-side dominant (5), but in case 1, the relative diameter of the left and right infrarenal IVC changed from one section level to another (see Figure 1C and D), which would be hard to rationalize as related to breathing or Valsalva effects.
IVC duplication has been described with cloaca1 exstrophy and horseshoe kidney. The incidence of horseshoe kidney is reported in different series as being between 1 in 600 to 1 in 1800 (6), and there is a male-female ratio of 3:l to 2:l. Associated genitourinary and extra-genitourinary anomalies are common (7). Horseshoe kidney results from fusion of the metanephric buds, likely secondary to failure of cephalic migration and normal rotation of the buds from their pelvic position during the fourth to sixth week. In the lo-mm embryo, the developing kidneys are cradled laterally by the large posterior cardinals. and anteromedially by the distal subcardinals. With normal renal enlargement and migration, the posterior cardinals are compressed against the developing lateral pelvic walls, and it has been postulated that this
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SMITH ET AL.
In summary, two cases of anomalous IVC in association with horseshoe kidneys are presented. Granting that these are only two cases, one can still speculate that with horseshoe fusion, impairment of the normal renal ascent and rotation could disturb the usual venous development, as described here. In theory, for example, this could result in persistence of a left supracardinal vein leading to the formation of a duplicated IVC; it could also possibly influence the persistence of the more ventral subcardinal or posterior cardinal veins, producing anomalies of the infrarenal IVC. The latter effect might also explain the frequent presence of retrocaval ureter that has been found in conjunction with preisthmus vena cava associated with horseshoe kidney. FIGURE 2. Preisthmic inferior vena cava (arrow) with horseshoe kidney (incidental right cyst is present).
tends to produce involution of the posterior cardinals, accompanied by enlargement of the anastomosing subcardinal system. Also, it has been noted that the left kidney is almost always ahead of the right in growth and length, which could explain the normal disappearance of the left posterior cardinals and dominance of the right venous system (8). A search of the literature revealed five cases of preisthmic vena cava associated with horseshoe kidney described only in operative findings, although not radiographically demonstrated (see Figure 2). These have been mainly in patients with horseshoe kidneys with right retrocaval ureter (6, 9). The etiology of retrocaval ureter is in some dispute-anomalous infrarenal IVC attributed to persistence of either the right posterior cardinal or the right subcardinal venous supply.
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6. Youssif M. Horseshoe kidney with retrocaval ureter. Eur Urol 1985;11:61-62. Grainger R, Lane V, Murphy DM. Horseshoe kidney-A review of the presentation, associated congenital anomalies and complications in 73 patients. Ir Med J 1983;76:315-317. Meucke EC, Cooke GT, Marshall VF. Duplication of the abdominal vena cava associated with cloaca1 exstrophy. J Urol 1972;107: 490-497. Kumeda K, Takamatsu M, Sone M, Yasukawa S, Doi J, Ohkawa T. Horseshoe kidney with retrocaval ureter; a case report. J Urol 1982;128:361-362.