Chapter 24 Disorders of Renal Function

Cystic and Obstructive Disorders Cystic disease of the kidney Simple and acquired renal cysts Medullary cystic disease Autosomal dominant polycystic kidney disease Obstructive disorders Hydronephrosis Renal calculi

Consequences of Dilation of Renal Tubules or Tract Expansion of the kidney with urine (hydronephrosis) Increased pressure inside the renal capsule Compartment syndrome compresses blood vessels inside kidney Renal ischemia Stasis of urine Risk of infection Stones

Hydronephrosis

Question Tell whether the following statement is true or false. Hydronephrosis is categorized as a disorder of glomerular function.

Answer False Rationale: Hydronephrosis is caused by a urinary obstruction, so it is considered an obstructive disorder. The glomerulus is not involved.

Renal Calculi Saturation theory: urine is supersaturated with stone components Matrix theory: organic materials act as a nidus for stone formation Inhibitor theory: a deficiency of substances that inhibit stone formation Four types of kidney stones: Calcium stones (i.e., oxalate or phosphate) Magnesium ammonium phosphate stones Uric acid stones Cystine stones

Urinary Tract Infections Bacteria usually enter through the urethra Host defenses include: Washout phenomenon Protective mucus Local immune responses and IgA Normal bacterial flora

Scenario: Mr. K is paraplegic. When in the hospital, he had a catheter Now he has a high fever and complains of joint and back pain He has pyuria and reports urgency BUN is 78 mg/dL PCR is 4.7 mg/dL Question: What complication are you most worried about? Why?

Question Tell whether the following statement is true or false: Urinary tract infections (UTIs) are usually caused by a virus.

Answer False Rationale: UTIs are most often caused by bacteria that enter through the urethra (most common) or the bloodstream.

Structure of the Glomerulus Glomerular capillaries and Bowman’s capsule are both made of epithelial cells sitting on a basement membrane They are so tightly attached to each other that they share one basement membrane The epithelial cells of Bowman’s capsule stand up from the basement membrane on foot processes, leaving pores between the feet for filtration Urine Epithelial cell Foot processes Basement membrane Blood in capillary

Immune Damage to the Glomerulus Antibodies to glomerular proteins Circulating immune complexes lodge in glomerulus

Glomerular Damage Proliferative: number of cells increase Sclerotic: amount of extracellular matrix increases Membranous: thickness of glomerular capillary wall increases All can decrease the efficiency of filtration Allow blood cells, lipids, or proteins to pass into the urine

Disorders of Glomerular Function Nephritic syndromes Proliferative inflammatory response Nephrotic syndrome Increased permeability of glomerulus Mixed nephritic and nephrotic responses Chronic glomerulonephritis Glomerular lesions associated with systemic disease

Nephritic Syndromes Proliferative inflammatory response RAA pathway activated; hypertension Inflammatory process damages the capillary wall Red blood cells escape into the urine Hematuria with red cell casts Hemodynamic changes decrease the GFR Azotemia (presence of nitrogenous wastes in the blood), oliguria

Nephrotic Syndrome Other proteins lost in urine: Immunoglobulins and complement  immune suppression Clotting and anticlotting proteins  thrombosis Proteins that carry other blood components  imbalances in blood components; altered drug dosages

Question Tell whether the following statement is true or false: Nephritic syndromes are characterized by blood in the urine.

Answer True Nephritic syndromes decrease the permeability of the glomerular capillary membrane, which results in hematuria, HTN, oliguria, and ↓ GFR.

Scenario: She has severe edema and frothy, cola-colored urine A woman has diabetes mellitus She has severe edema and frothy, cola-colored urine She has difficulty breathing, with crackles in both lungs She just finished a course of antibiotics for strep throat She is also taking corticosteroids for lupus-related arthritis Question: What are three reasons for her renal problems?

Scenario (cont.) A woman has diabetes mellitus and lupus and recently had strep throat. She has severe edema and frothy, cola- colored urine Question: The doctor says the only way to determine what has caused her glomerular disease is a renal biopsy. Why?

Scenario (cont.) Urinalysis show that she is producing: Urine with 500 mg protein/ day Contains blood and RBC casts High level of K+ Blood tests show: Hypoalbuminemia Slightly decreased K+ She has borderline hypertension Question: Does she have nephritic syndrome or nephrotic syndrome?

Tubulointerstitial Disorders Acute tubular necrosis Pyelonephritis Acute pyelonephritis Acute hypersensitivity to drugs Chronic pyelonephritis Drug-related nephropathies