Kidney and Urinary Tract Flashcards
Horseshoe Kidney
Conjoined kidneys usually connected at lower pole
MOST COMMON congenital renal anomaly
Kidneys are abnormally located in the lower abdomen as they get stuck on the Inferior Mesenteric Artery during its ascent from the pelvis
Renal Agenesis
Absent kidney formation
Unilateral = hypertrophy of existing kidney. Hyperfiltration increases the risk of renal failure later in life
Bilateral = get oligohydraminos with potter sequence (lung hypoplasia, flat face with low set ears, developmental defects of the extremities)
Incompatible with life
Potter Sequence
lung hypoplasia
flat face with low set ears
developmental defects of the extremities
See in congenital kidney diseases like bilateral renal agenesis and PKD
Dysplastic Kidney
NONINHERITED, congenital malformation of renal parenchyma characterized by cysts and abnormal tissue (cartilage)
usually unilateral but can be bilateral (especially on tests)
Polycystic Kidney Disease Autosomal Recessive
Inherited defect leading to bilateral enlarged kidneys with cysts in the RENAL CORTEX and MEDULLA
Autosomal Recessive = Presents in INFANTS as worsening renal failure and hypertension and possibly potter sequence. Associated with congenital hepatic fibrosis (get portal hypertension) and hepatic cysts
Polycystic Kidney Disease Autosomal Dominant
Inherited defect leading to bilateral enlarged kidneys with cysts in the RENAL CORTEX and MEDULLA
Autosomal Dominant = See in young ADULTS as hypertension (from increased renin), hematuria, and worsening renal failure.
Due to mutations in APK1 or APKD2.
Associated with berry aneurysm, hepatic cysts, and mitral valve prolapse
Medullary Cystic Kidney Disease
Inherited (aut DOM) defect leading to cysts in the MEDULLARY COLLECTING DUCTS
Parenchymal fibrosis results in SHRUNKEN kidneys and worsening renal failure
Acute Renal Failure
Hallmark is azotemia , increased BUN and Creatinine, and oliguria
Can be prerena;, postrenal, or intrarenal
Prerenal Azotemia
Due to decreased blood flow to kidneys → decreased GFR, azotemia and oliguria
activation of renin/angiotensin system ultimately leads to increased reabsorption of BUN (serum BUN:Cr ratio >15)
Tubular function remains intact so fractional excretion of 500mOsm/kg
Postrenal Azotemia
Obsturction of urinary tract causes a backpressure in the kidney that decreases GFR, azotemia, and oliguria
Early Stage = increased tubular back pressure forces BUN into the serum (serum BUN:Cr ratio >15) and Tubular function remains intact so fractional excretion of 500mOsm/kg
Long standing obstruction = get tubular damage and get decreased reabsorption of BUN (serum BUN:Cr 2% and inability to concentrate the urine (urine osm<500mOsm/kg)
Acute Tubular Necrosis
Injury and necrosis of tubular epithelial cells.
Necrotic cells slough off and plug the tubules and decrease GFR.
Oliguria, brown granular casts in urine, elevated BUN and creatinine, hyperkalemia, metabolic acidosis with increased anion gap
Reversible but generally need to be on dialysis for 2-3 weeks until the tubular/stable cells reenter the cell cycle and regenerate
Dysfunctional epithelium results in decreased reabsorption of BUN (serum BUN:Cr 2% and inability to concentrate the urine (urine osm<500mOsm/kg)
Etiology may be ischemic or nephrotoxic
Acute Tubular Necrosis from Ischemia
decreased blood supply results in necrosis of tubules
Often preceded by prerenal azotemia
PROXIMAL TUBULE and MEDULLARY SEGMENT of THICK ASCENDING LIMB are particularly susceptible to ischemic damage since these segments require a lot of ATP
Acute Tubular Necrosis from nephrotoxic
Toxic agents kill tubules
Proximal tubule is particularly susceptible
Causes include:
1) AMINOGLYCOSIDES
2) heavy metals = lead
3) Myoglobinuria = crush injury to muscle
4) Ethylene glycol = see OXALATE CRYSTALS in urine
5) Radiocontrast dye
6) Urate = tumor lysis syndrome (Prevent with hydration and allopurinol prior to chemo)
Acute Interstitial Nephritis
Drug induced hypersensitivity involving the interstitium and tubules results in acute renal failure
Causes include NSAIDS, PENICILLIN, and DIURETICS
Presents as oliguria, fever, and rash days to weeks after starting a med
EOSINOPHILS in urine
resolves with removal of drug but can progress to renal papillary necrosis
Renal Papillary Necrosis
Necrosis of renal papillae
Presents with gross hematuria and flank pain
Causes include:
1)Chronic analgesic abuse (long term phenacetin or aspirin use)
2) Diabetes mellitus
3) Sickle cell trait or disease
4) Severe acute pyelonephritis
Nephrotic Syndrome
Glomerular disorder characterized by proteinuria (>3.5g/day) resulting in:
Hypoalbuminemia = pitting edema
hypogammaglobulinemia = increased risk of infection
Hypercoaguable state = due to loss of antithrombin III
hyperlipidemia and hypercholesterolemia
Minimal Change Disease
CHILDREN
idiopathic usually but also associated with Hodgkin Lymphoma (overproduction of cytokines)
EFFACEMENT of PODOCYTES via CYTOKINES on electron microscopy
Seletive proteinuria = loss of albumin but not immunoglobulin
Excellent response to steroids
Normal glomeruli on H&E stain, no immune complex deposits so negative IF
Focal Segmental Glomerulosclerosis
HISPANICS and AFRICAN AMERICANS
usually idiopathic but also associated with HIV, HEROIN, and SICKLE CELL DISEASE
Focal in that only some glomeruli are affected and segmental in that of those glomeruli that are affected only parts of them show sclerosis on H&E
Effacement of foot processes on EM
No immune complexes depsotis so negative IF
Poor response to steroids and progresses to chronic renal failure
Membranous Nephropathy
CAUSCASIAN ADULTS
usually idiopathic but also associated with Hep B+C, solid tumors, SLE, or drugs like NSAIDs and penicillamine
Get a THICK glomerular BASEMENT MEMBRANE on H&E due to subepithelial immune complex deposition.
GRANNULAR IF, subepithelial “spike and dome” appearance on EM
Poor response to steroids and progresses to chronic renal failure
Membranoproliferative Glomerulonephritis
THICK glomerular BASEMENT MEMBRANE on H&E with “TRAM TRACK” appearance due to immune complex deposition
GRANULAR IF
Type I = subenothelial complex deposition. associated with Hep B and C. “tram track” appearance seen more clearly
Type II = dense intremembranous complex disease. Associated with C3 nephritic factor (an autoantibody that stabilizes C3 convertase, leading to overactivation of complement, inflammation, and low levels of circulating C3)
Poor response to steroids and progresses to chronic renal failure
Diabetes Mellitus Nephrotic Syndrome
High serum glucose leads to nonenzymatic glycosylation of the vascular basement membrane resulting in HYALINE ARTERIOSCLEROSIS
glomerular EFFERENT ARTERIOLE is affected more than afferent leading to high glomerular filtration pressure. Leads to hyperfiltration injury leads to microalbunemia.
Eventually progresses to nephrotic syndrome that is characterized by sclerosis of the mesangium with formation of Kimmesltiel-Wilson nodules