Chapter 12 Kidney and Urinary Tract Flashcards
What is the most common congenital renal anomaly?
Horseshoe kidney
What is a horseshoe kidney?
Conjoined kidneys usually connected at the lower pole
Where are horseshoe kidneys located and what happens during development that leads to this?
Kidney is abnormally located in the lower abdomen; horseshoe kidney gets caught on the inferior mesenteric artery root during its ascent from the pelvis to the abdomen
What is renal agenesis? is it usually unilateral or bilateral?
Absent kidney formation; may be unilateral or bilateral
What does unilateral kidney agenesis lead to?
Leads to hypertrophy of the existing kidney; hyperfiltration increases risk of renal failure (specifically FSGS)
What does bilateral renal agenesis lead to?
leads to Potter Sequence; oligohydramnios with lung hypoplasia, flat face (pressed up against wall of uterus) with low set ears, and developmental defects of the extremities
Is bilateral renal agenesis compatible with life?
NO
What is dysplastic kidney? What is it characterized by? is it inheritable?
Noninherited, congenital malformation of the renal parenchyma characterized by cysts and abnormal tissue (e.g. especially cartilage)
Is Dysplastic kidney unilateral or bilateral?
Usually unilateral can be bilateral
What does bilateral dysplastic kidney need to be differentiated from?
inherited polycystic kidney disease
What is polycystic kidney disease?
Inherited defect leading to bilateral enlarged kidneys with cysts in the renal cortex and medulla
How does the AR form of PKD present?
Presents in infants as worsening renal failure and hypertension; newborns may present with Potter sequence (due to decreased amniotic fluid)
What is the AR form of PKD associated with?
Congenital hepatic fibrosis (leads to portal hypertension) and hepatic cysts
How does the AD form of PKD present?
presents in young adults as hypertension )due to increased renin), hematuria, and worsening renal failure.
What is AD PKD due to? what is it associated with?
Due to mutation in the APKD1 or APKD2 gene; cysts develop over time. It is associated with berry aneurysm (many times cause of death) hepatic cysts, and mitral valve prolapse.
What is medullary cystic kidney disease? What is its inheritance pattern?
Inherited (AD) defect leading to cysts in the medullary collecting ducts
What does medullary cystic kidney disease lead to?
Parenchymal fibrosis results in shrunken kidneys (diff than PKD) and worsening renal failure
What is acute renal failure, how fast does it develop? general
Acute, sever decrease in renal function (develops within days)
What is the hallmark of ARF?
azotemia (increase nitrogenous waste products); increased BUN and creatinine, often with oligouria.
What three categories is ARF divided into?
Prerenal, postrenal, intrarenal
What is a normal BUN:Cr?
15
What is prerenal azotemia due to?
Due to decreased blood flow to kidneys (e.g. cardiac failure); common cause of ARF
What does decreased blood flow cause in prerenal azotemia?
results in decreased GFR, azotemia, and oliguria
Describe the BUN:Cr, FENa, and urine osmolarity in prerenal azotemia?
Resorption of fluid and BUN ensues (serum BUN:Cr >15); tubular functions remains intact (Fractional excretion of sodium [FENa] 500 mOsm/kg
Describe the pathophysiology behind the BUN:Cr ration in prerenal azotemia?
Low GFR causes increased levels of aldosterone and increase Na+ absorption along with H2O. As H2O resorption increases BUN will follow. Since Creatinine cannot be reabsorb, only BUN will rise and the ratio of BUN:Cr will also rise.
What is postrenal azotemia due to? what does this result in?
Due to obstruction of urinary tract downstream from the kidney (e.g. ureters). Decreased outflow results in decreased GFR, azotemia, and oliguria.
Describe the changes in serum BUN:Cr and tubular function in the early stages of postrenal azotemia?
During the early stage of obstruction, increased tubular pressure “forces” BUN into the blood (Serum BUN:Cr >15); tubular function remains intact (FENa < 1% and urine osm > 500mOsm/kg)
Describe the changes in serum BUN:Cr and tubular function with long standing postrenal obstruction?
With long standing obstruction, tubular damage ensues, resulting in decreases reabsorption of BUN (serum BUN:Cr ratio < 15), decreased reabsorption of sodium (FENa > 2%), and inability to concentrate urine (Urine osm < 500 mOsm/kg)
What is the most common cause of acute renal failure?
Acute tubular necrosis
What happens in acute tubular necrosis? what is seen in the urine?
Injury and necrosis of tubular epithelial cells (Intrarenal). Necrotic cells plug tubules; obstruction decreases GFR. Brown, granular casts are seen in the urine
What does dysfunctional tubular epithelium result in in acute tubular necrosis?
Results in decreases reabsorption of BUN (serum BUN:Cr ratio < 15), decreased reabsorption of sodium (FENa > 2%), and inability to concentrate urine (Urine osm < 500 mOsm/kg)
What are the two possible etiologies for acute tubular necrosis?
Ischemic and Nephrotoxic
What happens in ischemic acute tubular necrosis, what is it often preceded by?
Decreased blood supply results in necrosis of the tubules. Often preceded by prerenal azotemia
What two segments of the nephron are most susceptible to ischemic damage?
Proximal tubule and medullary segment of the thick ascending limb
What happens in nephrotoxic acute tubular necrosis and which segment of the nephron is most susceptible?
Toxic agents result in necrosis of tubules. Proximal tubule is particularly susceptible.
What are 6 causes of nephrotoxic acute tubule necrosis?
1 Aminoglycosides (most common)
2 heavy metals (e.g. lead)
3 Myoglobinuria (e.g. from crush injury to muscle)
4 ethylene glycol (associated with oxalate crystals in the urine)
5 Radiocontrast dye
6 Urate (e.g. tumor lysis syndrome)
What is done before starting chemo to prevent urate mediate tubular necrosis.
Hydration and allopurinol are used prior to initiation of chemotherapy to decrease risk of urate induvced ATN
What are the clinical features of Acute tubular necrosis? 3
1 oliguria with brown, granular casts
2 Elevated BUN and Creatinine
3 Hyperkalemia (due to decreased renal excretion ) with metabolic acidosis (Decrease in organic acid secretion results in anion gap acidosis)
How is Acute tubular necrosis treated? is it reversible?
Reversible, but often requires supportive dialysis since electrolyte imbalances can be fatal.
How long does oliguria persist after treatment of acute tubular necrosis? Why?
Oliguria can persist for 2-3 weeks before recovery; tubular cells (stable cells ) take time to reenter the cell cycle and regenerate.
What is acute interstitial nephritis?
Drug-induced hypersensitivity involving the interstitium and tubules; results in acute renal failure (intrarenal azotemia)
What are three common causes for acute interstitial nephritis?
NSAIDs, Penicillin, Diuretics
How does acute interstitial nephritis present?
Presents as oliguria, fever, and rash days to weeks after starting drug; EOSINOPHILS may be seen in the urine
What is the treatment for acute interstitial nephritis?
Resolves with cessation of the drug
What can acute interstitial nephritis progress to?
renal papillary necrosis
What is renal papillary necrosis?
Necrosis of the renal papillae
How does renal papillary necrosis present?
Gross hematuria and flank pain
Name 4 possible causes of renal papillary necrosis?
1 Chronic analgesic abuse (e.g. long-term phenacetin or aspirin use)
2 Diabetes Mellitus
3 Sickle cell trait or disease
4 severe acute pyelonephritis
Describe Nephrotic syndrome, what is it characterized by (1) and what does this result in (4)
Characterized by proteinuria (> 3.5 g/day) resulting in;
1 Hypoalbuminemia - pitting edema
2 Hypogammaglobulinemia - increased risk of infection
3 hypercoaguable state - due to loss of anithrombin III
4 Hyperlipidemia and hypercholesteremia - may result in fatty casts in urine ( blood becomes “thin” so liver throws in excess fat to beef it up)
What is the most common cause of nephrotic syndrome in children?
Minimal Change Disease
What is the etiology of minimal change disease and what may it be associated with (and why)?
Usually idopathic, may be associated with hodgkin lymphoma (massive overproduction of cytokines by RS cells cause effacement of the foot processes of the podocytes)
What can be seen on histology in acute tubular necrosis?
loss of nuclei and detachment of basement membrane
What is seen on H&E stain with minimal change disease?
Normal glomeruli; lipid may be seen in proximal tubule cells.
What can be seen on EM in MCD?
Effacement of foot processes
Is there immune complex deposition in MCD, what is seen on immunofluorescence?
No immune complexes, IF is negative
Describe the selective proteinuria in MCD?
Loss of albumin but not immunoglobulin
What is the treatment for MCD and how does it respond?
Excellent response to steroids
What is the cause of damage in MCD?
Cytokines produced by T cells
What is the most common cause of nephrotic syndrome in Hispanics and African Americans?
Focal Segmental Glomerulosclerosis (FSGS)
What is the etiology of FSGS? what may it be associated with?
Usually idiopathic, may be associated with HIV, Heroin use, and sickle cell disease
What is seen on histology in FSGS?
Focal (some glomeruli) and segmental (involving only part of the glomerulus) and sclerosis (Pink) on H&E stain
What is seen on EM in FSGS?
effacement of foot processes of podocytes
Are there immune complex depositions in FSGS? what is seen on IF?
No immune complexes, IF is negative
What is the treatment for FSGS, how does it respond and what might it progress to?
Poor response to steroids; progresses to chronic renal failure.
What does MCD progress to if it does not respond to steroids?
FSGS
What is the most common cause of nephrotic disease in causcasian adults?
Membranous nephropathy
What is the etiology of membranous nephropathy and what may it be associated with?
Usually idiopathic, may be associated with Hep B or C, solide tumors, SLE, or drugs (e.g. NSAIDs and penicillamine)
What is the most common cause of death in SLE, what type?
renal failure, most common is diffuse proliferative glomerulonephritis but can also present as membranous nephropathy
What is seen on H&E stain in Membranous nephropathy?
Thick glomerular membrane
What is membranous nephropathy due to?
Due to immune complex deposition
What pattern is seen on IF with Membranous nephropathy?
Granular
What is seen on EM in membranous nephropathy?
Subepithelial deposits with ‘spike and dome’ appearance
How is membranous nephropathy treated, how does it respond, what can it progress to?
Poor response to steroids; can progress to chronic renal failure
What is seen on H&E in Membroproliferative Glomerulonephritis?
Thick glomerular BM, often with ‘tram’track’ appearance
What is Membranoproliferative glomerulonephritis due to?
immune complex deposition
What pattern is seen on IF in membranoproliferative glomerulonephritis?
granular
What causes the ‘tram track’ appearance in membranoproliferative glomerulonephritis?
Messangial cells that hold together capillary loops undergo proliferation of cytoplasm which separates the deposits