Hypertension is the main manifestation of Page kidney and may develop rapidly after the causative event or may be slow in onset and occur a long time after the causative event. The history of trauma may not be obvious. In cases of recent perinephric bleeding, a flank hematoma may be seen. Otherwise, there are no significant abnormalities on physical examination in patients with Page kidney except for hypertension. Renal function is typically normal if compression of the kidney is unilateral since the contralateral normal kidney can compensate. Renal function may be impaired if the external renal compression is bilateral or there is compression of a single functioning kidney, e.g., transplant kidney.

Page kidney is most often diagnosed based upon imaging studies. Ultrasonography and computed tomography of the kidneys are the most frequently used modalities. Ultrasound has the advantage of being cheap, quick, easy to perform, easily available, and noninvasive. However, it can miss small subcapsular hematoma. CT scan of the abdomen has similar advantages and has the benefit of being able to detect small hematomas and is most frequently used.[4][5]

Renal vein renin determination can certainly prove activation of RAAS as the causative mechanism of hypertension but is frequently not done.

Activation of RAAS mediates hypertension in this condition, and hence the ideal agents for the treatment of hypertension are RAAS blockers.[3] Medical treatment of hypertension may be required for short period if the cause of renal compression resolves spontaneously or following intervention, e.g., resorption or evacuation of subcapsular hematoma. Intervention may be needed for larger, symptomatic or enlarging collections or those with poorly controlled hypertension. This may require open or percutaneous drainage of the compressing collection. If the collection has been of long standing, a fibrocollagenous shell may have formed, and this may require decapsulation of this shell or even nephrectomy. Elevation of blood pressure is permanent in some cases, and lifelong antihypertensive drug therapy may be needed.[6][7]

If the history of flank trauma is not available and the patient presents with hypertension, it would be impossible to diagnose Page kidney because there are no unique physical findings to suggest the disease. Imaging is the way to identify the disease. Elevated renin level indicates RAAS activation as the cause of hypertension and may be due to renal artery stenosis, juxtaglomerular cell tumor, malignant hypertension.

Page kidney or Page phenomenon results from external compression of the kidney and is a rare, treatable cause of secondary hypertension which is mediated by activation of the renin-angiotensin-aldosterone system (RAAS). External compression of the kidney may be due to a collection of blood or from some other source. Bleeding around the kidney may result from blunt trauma (sports injuries like football, hockey, other contact sports, motor vehicle accident, violence or fall), may be iatrogenic (following biopsy of native or transplant kidney, extracorporeal shockwave lithotripsy, ureteral surgery, sympathetic nerve block) or may be spontaneous (anticoagulation, AV malformation, tumor, vasculitis, pancreatitis). Non-bleeding causes of external compression include lymphoceles particularly around the transplanted kidney, urinoma, retroperitoneal paraganglioma or large simple cysts. Diagnosis is based on imaging studies, either abdominal ultrasound or computed tomography of the abdomen. Activation of RAAS mediates hypertension in this condition, and hence the ideal agents for the treatment of hypertension are RAAS blockers, pen or percutaneous drainage of the compressing collection. If the collection has been of long standing, a fibrocollagenous shell may have formed, and this may require decapsulation of this shell or even nephrectomy.[8][9][10]

Page kidney is a rare but potentially treatable and curable form of hyperension and requires awareness of the entity by primary care providers, nephrologists and other providers and a close coordination of care with radiologists in making the diagnosis and urologists in providing urologial options like percutaneous draiage or capsulectomy which may result in improvment in control or cure of hypertension.[2][6][8](Level 5)