What’s the difference between a Nephrologist and a Urologist?


Nephrologists are medical doctors who do not perform surgeries and specialize in the diagnosis and treatment of diseases of the kidney and urinary system, such as inflammation of the kidneys, chronic kidney disease, effects of high blood pressure and diabetes on the kidneys, side effects of medications on the kidneys and also complications of many other diseases on the way the kidneys function to filter the blood and keep it clean. Also nephrologists manage electrolyte disorders such as low or high sodium, potassium, calcium. Nephrologists also can manage but do not do surgery on patients who develop kidney stones and diagnose and prescribe medications to prevent them to come back again. Nephrologists also follow up patients with end stage kidney disease who already are on dialysis and prepare them to become candidates for kidney transplant, they also follow up patients already transplanted after the surgery.

Nephrologists can be board-certified in Nephrology through the board of Internal Medicine, which is recognized by the American Board of Medical Specialties.

Urologists are medical doctors who specialize in the diagnosis and treatment of diseases of the kidneys and urinary system in men and women and disorders of the male reproductive system. Urologists perform surgery and treat urination problems, such as difficulty in holding urine (incontinence), tumors, cysts, growths or stones of the urinary system, they also treat problems of the male reproductive system such as impotence (erectile dysfunction).

Urologists can be board-certified through the American Board of Urology, which is recognized by the American Board of Medical Specialties.

When to refer patients to a Nephrologist:

There are a lot of different reasons to refer patients from the primary care practice to a nephrologist, the following list can help you identified the most important problems that we can help you with:

  • Urine albumin-to-creatinine ratio (ACR) ≥300 mg/g (34 mg/mmol)
  • Hematuria not secondary to urological conditions
  • Inability to identify a presumed cause of CKD
  • eGFR below 60 or decline of more than 30 percent in fewer than four months without an obvious explanation
  • Difficult to manage complications such as anemia requiring erythropoietin therapy and/or IV Iron infusion, and abnormalities of bone and mineral metabolism requiring phosphorus binders or vitamin D preparations
  • Serum potassium greater than 5.5 meq/L, also low potassium levels, low or high sodium and calcium levels.
  • Difficult to manage drug complications
  • Resistant hypertension
  • Recurrent or extensive nephrolithiasis
  • Confirmed or presumed hereditary kidney disease

Nephrologists can assist primary care physicians and other specialists in the diagnosis and care of patients at all stages of CKD. These functions include determination of the cause of CKD, recommendations for specific therapy, suggestions for treatments to slow progression in patients who have not responded to conventional therapies, identification and treatment for kidney disease–related complications, and preparation for dialysis. Because patients with CKD are at risk for a diverse set of adverse outcomes (not just kidney failure), referral to other appropriate specialists (eg, cardiologists for those with complex CVD) should also be considered.

Also consider the following concepts:

A “Normal” Serum Creatinine Level May Not Be Normal.

Normal creatinine values may vary among different laboratories, and some patients with serum creatinine levels within the “normal” range may have substantial reduction in kidney function. If the estimated GFR falls below normal in someone whose values were normal before (i.e. eGFR < 60, being > 60 previously)

Patients With Decreased GFR or Proteinuria Should Be Evaluated to Determine the Cause; Positive Urine Dipstick Test Results for Protein Should Be Followed Up With a Spot Urine Protein to Urine Creatinine Ratio. Because it could represent a glomerular or tubular disease which may require a kidney biopsy and specialized treatment and follow up.

In Patients With Early-Stage CKD, Periodic Evaluation and Intervention Are Appropriate to Slow the Progression of Renal Disease and Avoid Its Complications. Emphasizing adequate blood pressure and blood sugar control and to avoid nephrotoxic drugs and volume depletion or dehydration. Also the early initiation of phosphate binders, diet control and vitamin D3 to delay the development of Secondary Hyperparathyroidism. Also the introduction of sodium bicarbonate to manage the metabolic acidosis and its complications.

Do Not Automatically Discontinue an ACEI or ARB Solely Because of a Small Increase in the Serum Creatinine or Potassium Level. Sometimes the benefits outweigh this minor changes in the serum creatinine.

Anemia in Patients With CKD Should Be Treated With Erythrocyte-Stimulating Agents Such as Recombinant Human Erythropoietin But Should Not Be Overtreated. We encourage the early referral to start treatment accordingly and to supplement with intravenous iron when indicated.

Although Most Patients With Hypertension Should Not Be Screened for Secondary Hypertension, Certain Clinical Clues May Suggest the Presence of an Underlying Cause That, When Addressed, May Resolve or Improve the Patient’s Hypertension. Specially if the patient is compliant with his/her medications and is already taking more than 3 drugs unsuccessfully. The nephrologist can help you determining the appropriate work up and follow up.

In Patients With Recurrent Stone Disease, an In depth Metabolic Evaluation Is Needed to Identify and Treat Modifiable Risk Factors, Thereby Preventing Further Episodes and/or Promoting Stone Dissolution. This is sometimes overseen and the appropriate diagnosis can help the patient to avoid further episodes and eventually any degree of loss of renal function.

Cystic disease is a relatively common finding and usually is incidental when a patient gets a radiological exam for other reasons. The nephrologist can help in managing those cases with multiple cysts and especially if associated to Polycystic Kidney Disease, because of the need to preserve renal function as long as possible. We do not perform surgery and usually simple cyst require observation alone and rarely need removal of such cyst. In the event it becomes complicated, such as tumor development the patient will need a Urology referral to handle that problem. As well as kidney masses or tumors, this is better managed by the Urologist, and without the delay, if referred to us first.

Back pain is most likely to be related to a musculoskeletal problem, most of kidney diseases are not going to be a source for back or “kidney” pain, unless a kidney stone is involved or a pyelonephritis (kidney infection) is happening to your patient with the systemic symptoms associated and in this case is likely a hospitalization is required for intravenous antibiotics. Do not delay the resolution of a back problem with a nephrology referral, consider the appropriate work up and referral to an orthopedic specialist first.


Staging of CKD

(Source UpToDate)

The purpose of CKD staging is to guide management, including stratification of risk for progression and complications of CKD. Risk stratification is used as a guide to inform appropriate treatments and the intensity of monitoring and patient education]. In patients who are diagnosed with CKD, staging of the CKD is done according to:

  • Cause of disease
  • Six categories of GFR (G stages)
  • Three categories of albuminuria (A stages)

Staging patients with CKD according to cause, GFR, and albuminuria enhances risk stratification for the major complications of CKD.

Cause of disease — Identifying the cause of kidney disease (eg, diabetes, drug toxicity, auto-immune diseases, urinary tract obstruction, kidney transplantation, etc.) enables specific therapy directed at preventing further injury. In addition, the cause of kidney disease has implications for the rate of progression and the risk of complications.

It can be difficult to ascertain the cause of kidney disease. In clinical practice, CKD is most often discovered as decreased eGFR during the evaluation and management of other medical conditions.

GFR — The GFR (G-stages) follow the original CKD classification scheme:

  • G1 − GFR >90 mL/min per 1.73 m2
  • G2 − GFR 60 to 89 mL/min per 1.73 m2
  • G3a − GFR 45 to 59 mL/min per 1.73 m2
  • G3b − GFR 30 to 44 mL/min per 1.73 m2
  • G4 − GFR 15 to 29 mL/min per 1.73 m2
  • G5 − GFR <15 mL/min per 1.73 m2 or treatment by dialysis

Since the original KDOQI classification was published, stage 3 CKD (a GFR of 30 to 59 mL/min per 1.73 m2) has been subdivided into GFR stages 3a and 3b to more accurately reflect the continuous association between lower GFR and risk for mortality and adverse kidney outcomes. Patients receiving treatment with dialysis are subclassified as GFR stage 5D to highlight the specialized care that they require.

Albuminuria — The three albuminuria stages follow familiar definitions of “normal”, “high” (formerly microalbuminuria), and “very high” (formerly macroalbuminuria and nephrotic range) albuminuria :

  • A1 − ACR <30 mg/g (<3.4 mg/mmol)
  • A2 − ACR 30 to 299 mg/g (3.4 to 34.0 mg/mmol)
  • A3 − ACR ≥300 mg/g (>34.0 mg/mmol)

The addition of albuminuria staging to GFR staging is new since the original KDOQI classification scheme was published. Albuminuria staging has been added because of the graded increase in risk for mortality, progression of CKD, and ESRD at higher levels of albuminuria, independent of eGFR, without an apparent threshold value. The increase in risk is significant for urine ACR values ≥30 mg/g, even when GFR is >60 mL/min per 1.73 m2, consistent with the current threshold value for albuminuria (≥30 mg/g) as a marker of kidney damage. An increased risk is also apparent with urine ACR levels between 10 and 29 mg/g (“high normal” albuminuria), suggesting that levels below 30 mg/g may also warrant increased attention.