Nephromegaly is the medical term used to describe the enlargement of one or both kidneys beyond their normal size. It is not a disease in itself, but rather a clinical sign that points to a potential underlying medical issue. This enlargement can be unilateral, affecting a single kidney, or bilateral, involving both. The normal length of an adult kidney is between 10 and 12 centimeters, and enlargement is noted when the size exceeds this range.
Associated Symptoms and Signs
The discovery of nephromegaly is often incidental, found during imaging tests conducted for other medical reasons, as the condition can be asymptomatic. When symptoms do arise, they are related to the stretching of the renal capsule, the fibrous tissue covering the kidney. This can lead to a persistent, dull ache in the flank area, which is the side of the body between the ribs and the hip.
In some cases, the enlarged kidney can be felt as a palpable mass in the abdomen during a physical examination. Other potential signs include hematuria, which is the presence of blood in the urine, giving it a pink, red, or brown appearance. Depending on the root cause of the enlargement, a person might also experience fever, which could indicate an infection, or develop hypertension (high blood pressure) as the kidney’s function becomes compromised.
Underlying Causes of Kidney Enlargement
A common cause of nephromegaly is a urinary tract obstruction, which leads to hydronephrosis. In this condition, urine cannot drain properly from a kidney, causing it to swell. Blockages can occur anywhere from the ureters to the bladder and may develop suddenly or over a longer period.
Genetic conditions are a significant factor, with Polycystic Kidney Disease (PKD) being a primary example where numerous cysts cause the kidneys to grow and impair their function. Infiltrative and inflammatory diseases also contribute to enlargement. For example, pyelonephritis (a kidney infection) causes swelling due to inflammation, while in amyloidosis, abnormal proteins build up in the kidney tissue. Cancers like lymphoma can also infiltrate the kidneys, leading to bilateral enlargement.
A solid tumor, such as renal cell carcinoma, causes unilateral enlargement as the mass grows and distorts the kidney’s structure. In compensatory hypertrophy, a single kidney enlarges to handle the entire workload of filtering blood when the other is absent, removed, or failing. Systemic diseases like diabetic nephropathy, a complication of diabetes, can also cause the kidneys to enlarge in its early stages due to the strain of filtering high levels of blood glucose.
The Diagnostic Process
Diagnosing nephromegaly and its cause begins with an evaluation of symptoms and a physical exam, where a provider may feel an enlarged kidney. Confirmation of enlargement relies on medical imaging. An ultrasound is frequently the initial imaging test used because it is non-invasive and can effectively visualize the kidneys to assess their size, structure, and the presence of any blockages or cysts.
For more detailed information, a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be ordered. These advanced imaging techniques provide cross-sectional views of the kidneys and surrounding tissues, which can help identify tumors, cysts, or the specific location of an obstruction. These scans help distinguish between the different causes of enlargement.
Laboratory tests are performed to assess kidney function. Blood tests measure levels of creatinine and blood urea nitrogen (BUN), which are waste products filtered by healthy kidneys. A urinalysis is also conducted to check for blood, protein, or white blood cells, which can indicate infection or disease. If the diagnosis remains unclear, a kidney biopsy may be performed to obtain a tissue sample for microscopic examination.
Approaches to Management and Treatment
Treatment focuses on addressing the specific medical condition causing the nephromegaly, not on reducing the kidney’s size. The management strategy is tailored to the diagnosed underlying cause. For example, if hydronephrosis is caused by a blockage like a kidney stone, treatment involves procedures to remove the obstruction and restore normal urine flow.
In cases where a bacterial infection such as pyelonephritis is the cause, a course of antibiotics is prescribed to eliminate the infection and reduce the associated inflammation. For genetic conditions like Polycystic Kidney Disease, management centers on controlling symptoms and slowing the progression of the disease. This includes medications to manage high blood pressure and strategies to handle pain from the cysts.
If the enlargement is due to a kidney tumor, treatment will depend on the type and stage of the cancer and may involve surgery, radiation therapy, or targeted drug therapies. For systemic diseases like diabetes, the goal is to manage the primary condition through blood sugar control and medications that protect kidney function.