The answer is d) adult onset polycystic kidney disease

The CT images provided (Figures 1 & 2) reveal massively enlarged kidneys, along with marked hepatomegaly, with innumerable discrete hypodense simple and complex cysts virtually replacing the normal renal tissue (leading to the abnormal renal function tests), and cystic involvement of the liver as well. The kidneys also contained a few hyperdense cysts, not uncommon in patients with adult onset polycystic kidney disease (PCKD). No true solid or suspicious lesions were identified. There were no signs of acute trauma within the abdomen.

PCKD is a genetic disorder characterized by development of numerous cysts in the kidneys. There are two forms of this disease. “Infantile PCKD” is a rare autosomal recessive disorder that typically begins in utero and leads to replacement of normal renal and hepatic tissue by innumerable tiny cysts (in comparison to the large cysts of the adult form) leading to renal enlargement and renal and liver function impairment and often marked hypertension. “Adult onset” PCKD is an autosomal dominant disease and the most common inherited kidney disease. Many patients with this condition live for decades without any symptoms, leading to the relative misnomer “adult onset,” since many of the cysts are present in early life but often are only discovered incidentally due to the lack of associated symptoms. The cysts may develop in the kidneys and many other organs, including the liver (leading to cirrhosis), pancreas (can cause pancreatitis), seminal vesicles (may cause infertility) and even the cerebral arachnoid surface. These patients are also prone to developing kidney stones (twice as common than in the general population), intracranial “berry” aneurysms (6-16%), hypertension and mitral valve prolapse (25%). The renal and hepatic cysts can grow quite large and the kidneys can enlarge to enormous proportions (25-30 cm, weighing over 13 ½ kilos each). The kidneys in the patient presented measured at least 20 cm in length on each side.

Once these patients develop end-stage renal failure, they may go on dialysis or undergo renal transplantation. The transplanted non-PCKD kidneys don’t develop similar cysts after transplantation. Patients with adult onset PCKD should also undergo genetic counselling prior to family planning, as the autosomal dominant nature of the disease means that with one parent with the disease, each child has a 50% chance of obtaining the PCKD gene. When our patient regained consciousness, he mentioned that the diagnosis of PCKD was already known, and that he had been planning to get a Medic-Alert bracelet indicating such, which is a good idea for all patients with this disease.

Renal cell carcinoma (RCC) comprises about 90-95% of renal neoplasms and although a cystic form has been described, the vast majority are solitary solid masses; in only 2% of cases are bilateral tumours present at diagnosis. RCC metastasizes to regional lymph nodes, lung, brain, bone but rarely liver. Bilateral renal cell carcinoma with liver metastases is not a viable option in this case. Hydatid disease is a parasitic infection caused by the cestode (tapeworm) genus Echinococcus. Humans become infected by ingesting meat of intermediate hosts (such as pigs, sheep, cattle, goats), which is infiltrated with the larvae of the parasite. The disease produces large complex cysts in many organs (especially liver and brain), which, if they rupture, can produce severe anaphylactic reaction and sudden death. Kidneys are not commonly involved. This would be an unlikely diagnosis in this case. Simple benign hepatic and renal cysts are extremely common. However, these lesions (although they can individually reach large sizes) do not typically result in overall enlargement of the kidneys and liver. This would be a very unlikely diagnosis in our case. Multiple renal and hepatic hematomas could, in theory, occur following significant trauma such as a car accident. However, on a non-contrast study they would appear as inhomogeneous hyperdense foci, likely with perihepatic and perinephric fat stranding as well, which is not the case in our patient. This, then, would be a very unlikely diagnosis as well.

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