Increase in Renal Volume

Checklist:

Increase in Renal Volume

• Is the increase in renal volume unilateral or bilateral?

• Are both kidneys visualized?

• Is there any urinary obstruction?

Fig.10.16 Demonstrated is a representative image of Ms. Peacock's CT. Can you help Paul?

Why Are They So Big?

It is almost impossible to obtain a history from Lydia Peacock (34) because of her mental impairment secondary to meningitis at a young age. Her young caretaker has only known her for three days. The referral note does not provide any more useful information: follow-up CT has been requested. Paul makes numerous attempts to contact the referring doctor, but he is away making house calls.

Paul finally gives up and postpones taking the history. He thinks the marked ascites is due to the liver metastases seen on previous CT images. But what is wrong with the kidneys (Fig. 10.16)?

• What is Your Diagnosis?

Compensatory renal hypertrophy: Compensatory hypertrophy occurs when there is only one kidney or when the other kidney is significantly impaired in its function. The cortical-medullary ratio of the affected kidney does not change.

Pyelonephritis: Pyelonephritis causes swelling of the kidney (Fig. 10.17). It is only an incidental finding for the radiologist, as imaging is not really required for the diagnosis. On CT there may be delayed contrast enhancement of the affected portion of the renal parenchyma on earlier images and retention of contrast on delayed images.

I Pyelonephritis

I Pyelonephritis

Fig. 10.17 The entire right kidney is enlarged and there is no differentiation between cortex and medulla. These findings point to advanced generalized pyelonephritis.

Lymphoma: This disease can present as hypoattenuating abnormal soft tissue in the perinephric space or in the renal parenchyma. It can also affect the entire kidney diffusely and cause an increase in size (see Fig. 10.8b).

Renal vein thrombosis: Renal vein thrombosis can cause venous congestion with associated swelling of the kidney.

Hydronephrosis: An increase in renal size is also seen in hydronephrosis secondary to urinary obstruction associated with enlargement of the renal pelvis (see Fig. 10.13a).

• Diagnosis: Paul is still not sure how to explain the bilateral renal enlargement. It is not until late in the afternoon that he gets some essential clinical information from Ms. Peacock's general practitioner. She has been on antibiotics for pyelonephritis over the last two days. The unfortunate findings of liver metastases and ascites are explained by her advanced breast cancer.

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