Figure 26. 99mTc-MAG3 scan obtained 4 hours post injection and showing gut activity. The transplant (arrowhead) is seen in the left iliac fossa. Irregular activity seen in the mid and lower abdomen on the right represents biliary excretion of the tracer into the gut and is usually present to some degree on delayed 99mTc-MAG3 views. Occasionally it can be so intense as to mimic a urine leak.

collecting system activity, and ultrasound must be relied upon to rule out ureteric obstruction. The most severe cases of harvesting injury may show poor perfusion, little uptake and high background levels even with 99mTc-MAG3.

Follow up studies in uncomplicated harvesting injury show progressive improvement over days to weeks. Beware of the case that shows improvement during the first week followed by a drop in perfusion or function. This may signal an additional complication such as rejection or cyclosporine nephrotoxicity.

Other complications in the early post-operative period include vascular catastrophe, hematoma, and urine leak. Renal artery or vein thrombosis presents as little or no perfusion or function, and may show the "black hole" sign, in which the transplant can be seen as a negative image with less activity than non-renal background (Fig. 24). This implies infarction of the graft. Hematoma presents as a photopenic area surrounding or adjacent to the graft. Hematoma can cause pressure on the kidney, impairing function directly or by causing ureteric obstruction. Urine leak

Figure 27. Renal trauma. 99mTc-glucoheptonate flow (A) and sequential images (B) on a young adult male injured in a car accident. There is very little flow and function in the right kidney. The large photopenic area inferior to the functioning upper pole represents infarcted kidney, hematoma and a small urinoma. The same patient was rescanned subsequently. Delayed images (C) show a normal left kidney, a right urine leak and a small amount of functioning right kidney.

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