Juxtaglomerular cell tumors, also known as reninomas, are uncommon renal tumors of the juxtaglomerular cells. The tumor cells secrete renin and often cause severe hypertension and hypokalemia.
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Epidemiology
Since their discovery, fewer than 200 cases of juxtaglomerular cell tumors have been described (c. 2024), and the true prevalence is unknown 6.
There is a female predominance (female-to-male ratio of 2:1), with a mean age of 27 years 6. However, all age groups are affected, with peak prevalence in the second and third decades of life.
Clinical presentation
Patients with a juxtaglomerular cell tumor present with headaches, dizziness, double vision, retinopathy, nausea, vomiting, and polyuria, with most of these features being attributable to hypertension or hypokalemia. Reninoma may also cause cerebrovascular accident and death secondary to hypertension 5. Hypertension is usually severe with a mean blood pressure of 201/130 mm Hg with 80% also presenting with hypokaelemia 6.
Pathology
Juxtaglomerular cell tumors are often well-circumscribed, yellow to grey-tan, with a complete or partial fibrous capsule usually observed. Histologically, the cytoplasm of tumor cells consists of renin and solid sheets of closely packed round to polygonal cells 5.
Radiographic features
Imaging findings are variable.
Ultrasound
hypoechoic mass
CT
typically solitary cortical or corticomedullary renal lesions with a mean diameter of 2cm-5cm 6
variable density with moderate enhancement during the late phase after contrast administration
MRI
Reported signal characteristics include
T1: iso-signal intensity
T2: high-signal intensity, although isointense and hypointense signal has been described 6
Nuclear medicine
juxtaglomerular cell tumors have not been proven to demonstrate fluorodeoxyglucose (FDG) avidity due to their slow growth and, therefore relatively low glucose uptake 6
Venography
Renal vein sampling may be performed with the intention of lateralizing renin production, although there has historically been reported variable success 6,7.
Accuracy of renal vein sampling may be improved preprocedure by enacting a low sodium diet (40mg/day) for 4 days prior and sampling before the patient sits up morning of procedure from a supine position overnight 6. These measures improve accuracy of lateralization because renin release follows a diurnal variability with responsiveness to postural change, sodium intake, catecholamines and certain medications 7.
Additionally stimulation of renin release intraprocedure with administration of furosemide, enalaprilat 0.04 mg/kg (max dose 2.5mg) or oral captopril 25mg also improves sensitivity 6,7.
A lateralization ratio of greater than 1.5, preferably with additional contralateral suppression, is considered most diagnostic 6.
Treatment and prognosis
Complete tumor resection by radical or partial nephrectomy is the best treatment for juxtaglomerular cell tumor. Anti-hypertensive agents can be used to manage hypertension until definitive therapy is planned. Hypertension however is progressive, with the effectivness of pharmacological RAAS blockage declining over time 6,7.
History and etymology
Juxtaglomerular cell tumor was originally described in 1967 by Robertson et al, but first named by Kihara et al. in 1968 1,6.
Differential diagnosis
On imaging consider other renal tumors such as