Kidney Function Tests (KFTs), also known as renal function tests, are a group of blood and urine tests used to assess the functioning of the kidneys.

1. 1. Blood Urea Nitrogen (BUN):
      • • Normal range: 7-20 mg/dL (2.5-7.1 mmol/L)

1. 1. Serum Creatinine:
      • • Normal range for adult males: 0.6-1.2 mg/dL (53-106 µmol/L)
      • • Normal range for adult females: 0.5-1.1 mg/dL (44-97 µmol/L)

1. 1. Estimated Glomerular Filtration Rate (eGFR):
      • • Normal range for adults: Greater than 90 mL/min/1.73m² to 120

1. 1. Serum Uric Acid:
      • • Normal range for adult males: 3.5-7.2 mg/dL (208-428 µmol/L)
      • • Normal range for adult females: 2.6-6.0 mg/dL (154-357 µmol/L)

1. 1. Serum Electrolytes:
      • • Sodium (Na+): 135-145 mEq/L
      • • Potassium (K+): 3.5-5.0 mEq/L
      • • Chloride (Cl-): 98-106 mEq/L
      • • Bicarbonate (HCO3-): 22-28 mEq/L

TERMINOLOGY

1. 1. Hematuria: Blood in urine

1. 1. Cylindruria: Casts in the urine

1. 1. Pyuria: Pus in urine 

1. 1. Leucocytouria: Leucocyte in urine

1. 1. Retention: Inability to void urine

1. 1. Incontinence: Involuntary voiding of urine

1. 1. Urgency: Increase in the frequency of urine

1. 1. Dysuria: Painful or burning urination

1. 1. Isothenuria: Same specific gravity of urine

1. 1. Glucosuria: Glucose in the urine

1. 1. Cystinuria: Cysteine in urine

1. 1. Oxaluria : Oxalic acid in urine

1. 1. Bacteriuria: Bacterias in urine

1. 1. Hemoglobinuria: Hemoglobin in urine

Renal System

Urinalysis

Use dipstick in freshly voided urine specimen to assess the following:

1. Specific Gravity: Range is 1.001-1.030

1. 1. values <1.010 reflect dilute urine, values >1.020 reflect concentrated urine

1. 1. value usually 1.010 (isosthenuria: same specific gravity as plasma) in ESRD

2. pH:  urine pH is normally between 4.5-7.0; if persistently alkaline, consider

1. 1. ■ RTA

1. 1. ■ UTI with urease-producing bacteria (e.g. Proteus)

3. Glucose: negative in normal urine. freely filtered at the glomerulus and reabsorbed in the proximal tubule: causes of glycosuria include:

1. 1. Hyperglycemia >9-11.1 mmol/L leads to filtration that exceeds tubular resorption capacity

1. 1. Increased GFR (e.g. pregnancy – the proximal convoluted tubule is unable to reabsorb the glucose and amino acids)

4. Protein: normally negative, dipstick only detects albumin; other proteins (e.g. Bence-Jones, Ig, Tamm-Horsfall) may be missed

1. 1. Microalbuminuria (morning ACR of 2.0 – 20 mg/mmol) is not detected by standard dipstick; greater than these ranges would be macroalbuminuria

1. 1. Gold standard: 24 h timed urine collection for total protein 

5. Leukocyte Esterase: Enzyme found in WBC and detected by dipstick shows the presence of WBCs indicates infection (e.g. UTI) or inflammation along the urinary tract including prostate, bladder, ureter, pelvis, and interstitium (e.g. AIN)

6. Nitrites: endogenous nitrates in urine are converted to nitrites by some bacteria (most commonly E. coli), with high specificity but low sensitivity for UTI

7. Ketones:  positive in alcoholic/diabetic ketoacidosis, prolonged starvation, fasting

8. Hemoglobin: positive in hemoglobinuria (hemolysis), myoglobinuria (rhabdomyolysis), and true hematuria (RBCs seen on microscopy)

Microscopy

Erythrocytes: hematuria = >2 RBCs per HPF

1. 1. Dysmorphic RBCs and/or RBC casts suggest glomerular bleeding (e.g. proliferative GN)

1. 1. Isomorphic RBCs or no casts suggest extraglomerular bleeding (e.g. bladder cancer)

Leukocytes: pyuria = greater than the upper limit of normal: >4 WBCs per HPF, indicates inflammation or infection

Zimnitsky test evaluates urine volume and concentration over a 24-hour period, providing information about kidney function and fluid balance. 

The Nechiporenko test, on the other hand, examines the urine sediment microscopically to detect abnormal cellular elements and diagnose conditions such as urinary tract infections and kidney inflammation.

Diagnostics In Nephrology

Diagnostics in nephrology involve various tests and procedures to evaluate kidney function, diagnose kidney diseases, and monitor the progression of kidney conditions. Here are some common diagnostic methods used in nephrology:

1. 1. Urinalysis: This test analyzes a urine sample to assess various parameters, including the presence of blood, protein, glucose, or other abnormalities. It helps in detecting kidney infections, urinary tract disorders, and kidney damage.

1. 1. Blood Tests:
      • • Kidney Function Tests: These include blood urea nitrogen (BUN), serum creatinine, and estimated glomerular filtration rate (eGFR) to assess overall kidney function and determine the stage of kidney disease.
      • • Electrolyte Levels: Blood tests measure levels of sodium, potassium, chloride, bicarbonate, and other electrolytes to evaluate the balance and function of these important substances in the body.
      • • Serum Uric Acid: Elevated levels of uric acid may indicate conditions like gout or impaired kidney function.

1. 1. Imaging Studies:
      • • Ultrasound: This non-invasive procedure uses sound waves to create images of the kidneys, helping to detect abnormalities, such as kidney stones, cysts, or tumors.
      • • CT Scan: A computed tomography (CT) scan provides detailed cross-sectional images of the kidneys and helps identify structural abnormalities or complications like tumors.
      • • Magnetic Resonance Imaging (MRI): This imaging technique uses a magnetic field and radio waves to produce high-resolution images of the kidneys and surrounding structures.

1. 1. Kidney Biopsy: A kidney biopsy involves the removal of a small sample of kidney tissue for examination under a microscope. It helps in diagnosing kidney diseases and determining the extent of damage or inflammation.

1. 1. Renal Scintigraphy(Radioisotope Renography): This nuclear medicine test involves injecting a small amount of radioactive material into the bloodstream to assess the functional capacity of both kidneys

1. 1. Genetic Testing: In some cases, genetic testing may be recommended to identify inherited kidney disorders or determine the risk of developing certain kidney diseases.

1. 1. Specialized Tests: Additional tests may be performed to evaluate specific kidney conditions, such as autoimmune markers, complement levels, or specific antibody tests for glomerulonephritis or autoimmune kidney diseases.

1. 1. Urography: Best to visualize the Ureter and renal pelvis system

• • Retrograde urography: It is useful for assessing ureteral and bladder abnormalities. 

• • Intravenous Pyelogram (IVP): Also known as intravenous urography (IVU), an IVP or Excretory urography, It is useful for assessing kidney function, detecting stones, tumors, or other urinary tract abnormalities. Usually Used To visualize developmental anomaly of renal Pelvis calyx system.

• • Micturating cystourethrography: to clarify the recurrent cause of urinary infection recurrence.

Key Points To Remember