Kidney Dysfunctions

• RAAS system

  • Kicks in during decrease in perfusion to try to improve blood pressure and perfusion to kidneys
• ADH

  • Balances fluid/sodium, same role as RAAS in improving perfusion and fluid volume in the kidneys
• Common laboratory tests of kidney function

  • Urine tests
  • Blood tests (BUN, creatinine)
• Urine tests

  Show how well the kidneys are filtering and doing their job
• Blood tests

  Kidney function tests
• Common manifestations of kidney disease

  • Urinary tract infections (UTIs)
  • Hydronephrosis
  • Polycystic kidney disease (PCKD)
  • Glomerular disorders
  • Renal calculi
  • Renal neoplasms
• UTI

  Upper UTI (pyelonephritis) - infection of renal parenchyma and renal pelvis

  Lower UTI (cystitis) - inflammation/infection of bladder lining
• UTI risk factors

  • Length of female urethra
  • Hygiene (e.g. wiping back to front)
  • Obstructive/reflux
  • Neurogenic bladder
  • Diabetes mellitus
  • Catheterization
  • Trauma
  • Sexual activity
  • Age (older adults, preschool females, pregnancy)
• UTI manifestations


  Fever, chills, flank pain, frequency urinating, dysuria (upper UTI)

  Fever, chills, nausea/vomiting, anorexia (pyelonephritis)

  Dysuria, pain, cloudy urine, frequency, urgency (cystitis)

  Fever, irritability, poor feeding, vomiting/diarrhea, ill appearance (child)

  Lethargy, anorexia, confusion/anxiety (adult)
• Hydronephrosis


  Interference with flow of urine = urine stasis (infection) + structural damage

  Can be complete or partial: decreased GFR, ischemic, fluid retention
• ADPKD

  Autosomal dominant polycystic kidney disease

  Kidneys filled with cysts, reducing kidney function, leading to decreased GFR, hypertension, pain
• ARPKD

  Autosomal recessive polycystic kidney disease

  Similar to ADPKD but occurs in children, with declining kidney function due to cysts
• APSGN

  Acute post-streptococcal glomerulonephritis

  Immune complex damages the glomeruli, leading to proteinuria, hypertension, hematuria, edema
• Nephrotic syndrome


  Increased capillary wall permeability to serum proteins, leading to large protein loss, edema, reduced colloidal osmotic pressure
• Renal calculi (nephrolithiasis)


  Stones that obstruct urine flow, leading to urine stasis, predisposing to infection and structural damage

  Manifestations: intense pain, nausea/vomiting, hematuria
• Renal neoplasms

  Wilms' tumor in children - tumor in the kidneys
• Many drugs can reduce renal blood flow, leaving the kidneys vulnerable to damage
• AKI (acute kidney injury)

  Acute reduction in kidney function, disrupting fluid, electrolyte, and acid-base balance

  Indicator is azotemia (elevated urea/nitrogen in blood)
• CKD (chronic kidney disease)


  Chronic, irreversible loss of kidney function developing over time

  Complications: hypertension, cardiovascular disease, uremic syndrome, metabolic acidosis, electrolyte imbalances, bone/mineral disorders, malnutrition, anemia, pain, depression
• Causes of renal failure

  • Prerenal (decreased perfusion)

  Intrarenal (direct kidney disease processes, medication effects)

  Postrenal (obstructive/blockage after the kidneys)
• Hemodialysis


  Blood is filtered outside the body through a machine to remove waste and excess electrolytes
• Peritoneal dialysis

  Dialysis fluid is instilled into the peritoneal cavity to remove waste and excess fluid
• Functions of the Kidney

  • Endocrine functions
  • Vitamin D activation
  • Erythropoietin production and regulation
  • Regulation of acid-base balance
  • Regulation of water and electrolyte balance
  • Regulation of blood volume and pressure
  • Filtering of waste products
• RAAS system

  Renin-Angiotensin-Aldosterone System
• ADH (Anti-Diuretic Hormone)

  • Increases in blood volume causing diuresis
  • Decreases in blood volume which reduces urine output to conserve fluid
  • Secreted when osmoreceptors in the hypothalamus detect high osmolality which makes the tubule permeable to water and allows water to be reabsorbed from the urinary filtrate
  • Insufficiency of ADH causes diabetes insipidus
• Aldosterone

  • Increases reabsorption of Na and water to increase blood volume
  • Released in response to renin
  • Renin is released when decreased blood flow to the kidney, decreased sodium levels, and activation of sympathetic nerves
  • Causes Na to be reabsorbed increasing blood volume which increases BP causes increase blood flow to the kidneys
  • Renin and aldosterone stop once BP is restored
• Common laboratory tests of kidney function

  • Urine tests: Urinalysis, 24-hour urine
  • Blood tests: BUN, creatinine, GFR
• Urinalysis


  • Normal urine is clear, pale, yellow to amber, and slightly acidic
  • Tests for SG, glucose, ketones, protein, sediment (casts-cells such as RBC, WBC other cells)
• 24-hour urine

  • Total quantity of substances excreted in a day
  • Urine osmolality and specific gravity vary over the day depending on fluid intake
  • Specific gravity range: 1.010 (dilute) - 1.035 (concentrated)
• Serum Creatinine

  • More reliable indicator of kidney function than BUN
  • Creatinine is the end-product of muscle metabolism that is excreted by the kidney exclusively
  • Expect an increase in Cr of 1-1.5 mg/dl per day in acute renal failure
• BUN


  Urea is the end product of protein metabolism, Rises with a decrease in renal function
• Age-related effects on the kidneys

  • Infants: GFR less than half of adult rate, immature kidneys cannot concentrate urine, reach kidney maturity in about 2 years
  • Adults: Kidneys diminish in size and function, decreased glomeruli/nephrons and decreased renal blood flow, susceptible to kidney damage from medications, decrease GFR over time
• UTI Risk Factors

  • Female: length of the urethra
  • Hygiene (wipe front to back)
  • Obstruction/reflux contributes to stasis (enlarged prostate)
  • Neurogenic bladder (incomplete emptying)
  • DM
  • Catheterization
  • Trauma, sexual activity
  • Age: older adult, preschool female
• Pyelonephritis

  • Upper UTI Infection of renal parenchyma and renal pelvis
  • More serious and more likely to lead to renal failure over time
  • Can get it from the bloodstream but more typically from ascending the urinary tract
• Acute Pyelonephritis

  • Usually unilateral, right kidney more often
  • Manifestations: CVA tenderness(classic sign), fever, chills, N/V, anorexia, dehydration
• Chronic Pyelonephritis

  • Characterized by small atrophied kidneys with diffuse scarring
  • Multiple acute pylori infection causing chronic pylo
  • For each acute infection, damage occurs, scarred kidneys over time
  • Manifestations: Vague, inconsistent or similar to those of acute pyelonephritis, present with abdominal/flank pain, fever, malaise
• Cystitis

  • Lower UTI inflammation/infection of the bladder lining
  • Can become complicated (caused by more obscure or difficult-to-treat bacteria)
  • Etiology: Caused by E.Coli
  • Manifestations: frequency, urgency, dysuria, suprapubic pain, and cloudy
  • Children: fever, irritability, poor feeding, vomiting, diarrhea, and ill appearance
  • Older adults: lethargy, anorexia, confusion, anxiety
• Catheter-induced UTI (CAUTI)

  • A most frequent cause of gram-negative infections in hospitalized
  • Risk of introduction of pathogen during insertion
  • Risk of bacteria growing the longer catheter is in
  • Risk Factor: Hygiene
• Hydronephrosis

  • Swelling of the kidney due to build of urine
  • Usually, one of both kidneys is affected
  • Decreased GFR
  • Ischemic kidney damage because of increased intraluminal pressure
  • Fluid retention
  • Compensatory hypertrophy of other kidney
  • Symptoms of kidney failure
• Types of Polycystic Kidney Disease

  • ARPKD: Infants and children (rare)
  • ADPKD: Adults