General pathology & physiology Flashcards
homeostatic mechanism that protects from salt and volume wasting by the macula densa sensing NaCl concentration in the filtrate leaving the loop of Henle. If the [NaCl] is high, it signals the afferent arteriole to constrict, decreasing GFR.
tubuloglomerular feedback
referred to as the “diluting segment of the nephron” since it is impermeable to water but reabsorbs NaCl, producing dilute urine
DCT and thick ascending limb
location where final adjustments to electrolyte composition are made, under the influence of aldosterone; AVP (ADH) modulates the water permeability of this portion of the nephron
collecting duct system
- concentration of NaCl in the interstitium by active transport in the TAL (no water permeability)
- water is extracted from the filtrate in the collecting duct, under the influence of ADH
- urea is concentrated in the filtrate, since the cortical & outer medullary ducts have low permeability to urea
- urea diffuses out of the inner medullary collecting duct, since it is permeable
- urea is trapped by countercurrent exchange in the vasa recta
- urea in the medullary interstitium attracts water from the tubular fluid, concentrating the NaCl within the tubule (thin descending limb)
- NaCl diffuses out of the thin ascending limb, contributing to the hypertonicity of the medullary interstitium
passive countercurrent multiplier hypothesis
Major Prerenal Causes of Acute Renal Failure
- volume depletion (GI, renal, third space losses)
- CHF or valvular heart disease
- hepatorenal syndrome is advanced cirrhosis
- bilateral renal stenosis (after ANG II inhibitor)
- drugs that interfere with autoregulation (NSAIDs)
- Shock due to fluid loss, sepsis, cardiac failure (progressing to ATN)
Major Causes of Intrinsic Renal Disease w/ ARF
Glomerular Disease Tubulointerstitial disease (ATN, postischemic, drug toxicity, intratubular obstruction) Vascular Disease (vasculitis, atherothrombi to the kidney)
Major Postrenal Causes of ARF
Prostatic disease in men
pelvic or retroperitoneal malignancy
these are conditions that cause urinary obstruction
Hematuria
mild to moderate proteinuria
HTN
Due to glomerular injury
nephritic syndrome
>3.5 g/day proteinuria hypoalbuminemia edema hyperlipidemia lipiduria due to glomerular injury
nephrotic syndrome
manifests as polyuria and electrolyte abnormalities
renal tubular defects
acute nephritis
proteinuria
acute renal failure
rapidly progressing glomerulonephritis
uremia progressing for years
chronic renal failure
subepithelial accumulation of Ig deposits causing diffuse thickening of the glomerular capillary wall
Causes nephrotic syndrome in adults
85% idiopathic but remainder caused by SLE, NSAIDs, infections, malignancy
Membranous nephropathy
What underlies most glomerular injury?
immune mechanisms
elevation of BUN and creatinine in the blood
azotemia
characterized by failure of renal excretory function with a host of metabolic and endocrine alterations resulting from renal damage, including secondary involvement of the GI system, peripheral nerves and heart
uremia
oliguria or anuria with recent onset of azotemia; can result from glomerular, interstitial or vascular injury or acute tubular injury
acute renal failure
dominant features are polyuria, nocturia and electrolyte disorders
renal tubular defects
Ex: cystinuria, RTA, lead nephropathy
constituents of the GBM
type IV collagen, laminin, proteoglycans (mostly heparan sulfate), fibronectin, entactin
contractile, phagocytic cells, capable of proliferation capable of laying down both matrix and collagen, also secrete biologically active mediators. These cells support the glomerular tuft and are between capillaries (p910R)
mesangial cells
accumulations of proliferating parietal cells and infiltrating leukocytes, from immune or inflammatory injury; response is elicited by fibrin leaking into the urinary space (fibrin deposition is stimulated by macrophage procoagulant activity)
crescent formation
thickening of basement membrane due to increased synthesis of its protein components
diabetic glomerulosclerosis
histologic alterations of glomerulopathies
hypercellularity
basement membrane thickening
hyalinosis and sclerosis
accumulation of extracellular collagenous matrix, confined to the mesangial areas or involving the capillary loops or both
sclerosis
Primary glomerulopathies that present with nephrotic syndrome
membranous glomerulopathy
minimal-change disease
focal segmental glomerulosclerosis
membranoproliferative glomerulonephritis type I
Primary glomerulopathy that presents with nephritic syndrome
postinfectious glomerulonephritis
Note about GFR prediction of ESRD (p916R)
Once renal disease causes GFR to decrease to 30-50% of normal, progression to ESRF proceeds at a relatively constant rate, independent of the original stimulus
IgA deposition in the mesangium, sometimes with IgG and C3 in a child age 3-8yr
purpuric skin lesions on arms, legs & buttocks
nephritic or nephrotic syndrome
subepidermal hemorrhages
may have recurrent hematuria for years
Henoch-Schonlein Purpura
Thickened capillary loops and glomerular cell proliferation => double-contour appearance => tram-track appearance
50% progress to chronic renal failure in 10 years
Glomeruli appear lobular due to mesangial cell proliferation.
Type I: Ag/Ab complex deposition and complement activation with subENDOthelial deposits
Type II: (dense deposit disease) alternative complement pathway activation with C3 deposits on either side of the GBM
Membranoproliferative Glomerulonephritis
visceral epithelial damage (effacement or detachment) in affected glomerular segments and due to cytokine or mutation of proteins of slit diaphragm
sclerosis of some but not all glomeruli and only a portion of the capillary tuft is involved
non-selective proteinuria, hematuria, reduced GFR, HTN
progresses to chronic renal failure in 20%
Focal Segmental Glomerulosclerosis
accounts for 20% of steroid-resistant nephrotic syndrome in children with mutation of a protein of the slit diaphragm
FSGS with mutation of NPHS2 (encodes podocin)
most common cause of glomerulonephritis worldwide and major cause of recurrent hematuria
Increased secretion of mucosal IgA in response to ingested or inhaled antigens
Present with gross hematuria following respiratory, GI or urinary infection
IgA deposition in the mesangium and activation of alternate complement pathway
IgA Nephropathy = Berger disease
Hematuria progressing to chronic renal failure
Symptoms at age 5-20 yr with RF at 20-50 yr in men
Nerve deafness
lens dislocation
cataracts
corneal dystrophy
Defective assembly of Type IV collagen in the GBM (85% are X-linked with mutations in alpha5 chain & autosomal forms are in alpha3 & alpha4)
Lab: increased IgA & red cell casts
GBM thinning and interstitial cells are stuffed with fats & mucopolysaccharides
Alport Syndrome = hereditary nephritis
asymptomatic hematuria with diffuse thinning of the basement membrane
normal renal function
NO involvement of hearing or eyes
associated with mutations in alpha3 and alpha4 chains of type IV collagen
Thin Basement Membrane Lesion = Benign Familial Hematuria
Common end stage of poststrep GN, RPGN, membranous GN, FSGS, MPGN, IgA nephropathy
kidneys are symmetrically contracted with diffuse granular surfaces and thinned cortex
Clinical: HTN, uremia, pericarditis, uremic gastroenteritis, secondary hyperparathyroidism, nephrocalcinosis, renal osteodystrophy
must do dialysis or renal transplant
Chronic Glomerulonephritis
Nonenzymatic glycation of proteins of the GBM
Hemodynamic changes resulting in increased GFR, increased GC pressure and glomerular hypertrophy
Glomerular disease leading to ESRF
Glomerular disease leading to proteinuria with or without nephrotic syndrome
Includes: hyalinizing arteriolar sclerosis, increased susceptibility to pyelonephritis and papillary necrosis
See: basement membrane thickening, diffuse mesangial sclerosis, NODULAR glomerulosclerosis
Diabetic nephropathy
Congo red + fibrillary protein deposit in the mesangium
proteinuria severe enough to cause nephrotic syndrome
eventually obliterate the glomerulus completely
Ig light chain most common
Dialysis-associated protein deposit: alphabeta2m (beta2 microglobulin which cannot be filtered by the dialysis membrane deposits in synovium, joints, tendon sheaths) -> presents as carpal tunnel
Amyloidosis
Wire loop lesions suggest active disease ANA to DNA female presents age 20-30 yr typically failure of self-tolerance presents as diffuse proliferative glomerulonephritis in 35-60%
SLE
Characterized by 3 Clinical stages:
1. ischemic event (36 hrs)
2. maintenance stage: 40-400 ml/day urine output, salt and water overload, increased BUN, hyperkalemic metabolic acidosis, uremia with dialysis initiation
3. Recovery: urine output increasing up to 3L/day, hypokalemia, vulnerability to infection
Morph: flattened epithelium with evidence of regeneration and mitotic figures; loss of prox tubule brush borders
hyaline and pigmented granular casts in distal and collecting tubules
Acute Tubular Necrosis
Organisms that cause acute pyelonephritis
E coli Proteus Klebsiella Enterobacter staph (in immunocompetent) polyomavirus, CMV and adenovirus in immunocompromised
causes pyelonephritis in kidney allografts
viral infection of tubule epithelial cell
nuclear enlargement with inclusions
polyomavirus
tubulointerstitial inflammation, renal scarring, and dilated deformed calyces
Most frequently caused by vesicouretal reflux diagnosed when investigating childhood HTN
chronic pyelonephritis
Drugs that can cause acute interstitial nephritis
PCNs, rifampin, diuretics (thiazide), NSAIDs, allopurinol, cimetidine
see fever, rash, and renal abnormalities ~15 days after exposure
papillary necrosis followed by cortical tubulointerstitial nephritis; associated with phenacetin mixed with aspirin, caffeine, acetaminophen, codeine
Glutathione is depleted with ROS generation
analgesic nephropathy
hyperuricemia causing acute uric acid nephropathy: precipitation of uric acid crystals in collecting ducts
seen in chemotherapy patients with leukemia lymphoma: uric acid released from apoptotic tumor cells as they are broken down
leads to obstruction and acute renal failure, chronic urate nephropathy and nephrolithiasis
urate nephropathy
pink to blue amorphous masses fill and distend tubular lumens as a complication of a tumor
hypercalcemia, hyperuricemia, obstruction of ureters
Can erode the tubules and cause granulomatous reaction
light chain casts
Light-chain Cast Nephropathy = Myeloma Kidney
vascular insult causes endothelial injury, platelet deposition, increased vascular permeability leading to fibrinoid necrosis with intravascular thrombosis
small pinpoint petechial hemorrhages on cortical surface from rupture of arterioles or glomerular capillaries
“flea-bitten kidney”
BP: systolic > 200 mm Hg and diastolic > 120 mm Hg
hyperplastic arteriopathy (onion-skinning)
Hematuria, proteinuria, papilledema, encephalopathy, cardiovascular abnormalities, eventual renal failure
malignant accelerated nephrosclerosis
Manifests clinically with bruit, ELEVATED PLASMA RENIN
Male > female
most commonly caused by atheromatous plaque at the origin of the renal artery
unilateral renal artery stenosis
Seen most frequently after obstetrical emergency such as abruptio placentae, septic shock, or extensive surgery
Fatal if bilateral and symmetric; if patchy survival is possible
Ischemic necrosis
may cause sudden anuric and uremic death
Diffuse Cortical Necrosis
sporadic disorder caused by abnormality in metanephric differentiation and characterized by persistence of abnormal structures: cartilage, undifferentiated mesenchyme, immature collecting ductules and abnormal lobar organization
Most cases are associated with ureteropelvic obstruction, ureteral agenesis or atresia
unilateral or bilateral & almost always cystic dysplasia
If unilateral, the other kidney has normal function.
multicystic renal dysplasia
AD hereditary disorder characterized by multiple expanding cysts of both kidneys, ultimately destroying the renal parenchyma and causing renal failure
Requires mutation of both alleles.
Universally bilateral
Function retained until 4th or 5th decade, since only parts of the nephrons are initially involved
Mutations of PKD1 in 85%
polycystic kidney disease
PKD1 encodes polycystin-1 which has been localized to the distal nephron
PKD2 encodes polycystin-2 which is in all segments of the nephron and in other tissues
Polycystin-1 and polycystin-2 are in the primary cilium which is a mechanosensor that monitors changes in fluid flow & shear stress
inheritance of PKD that is perinatal, neonatal, infantile, juvenile and associated with hepatic lesions
ARPKD
gene mutation associated with ARPKD
PKHD1 which encodes for fibrocystin which is localized to the primary cilium of tubular cells and highly expressed in adult and fetal kidney, liver, and pancreas
Dilation of the renal pelvis and calyces associated with progressive atrophy of the kidney due to obstruction of outflow or urine.
Renal calyces dilate and high pressure in the pelvis is transmitted to the collecting ducts into the cortex, causing renal atrophy
-impaired tubular concentrating ability initially followed later by fall in GFR
hydronephrosis
can cause obstruction of urinary flow or produce ulceration & bleeding
renal calculi
4 types of renal calculi
- calcium oxalate
- magnesium ammonium phosphate (staghorn = triple)
- uric acid
- cystine
Most common type of renal cell carcinoma
somatic mutations in VHL gene
(loss, hypermethylation, or inactivated/mutated)
clear cell carcinoma
other types of carcinoma associated with VHL:
papillary(10-15%) and chromophobe (5%)
What does VHL gene encode?
Protein that targets other proteins for degradation, especially HIF-1.
Remember the role of HIF in renal cell carcinoma. The patient in the case had polycythemia due to elevated HIF.
risk factors for renal cell carcinoma
tobacco obesity (female) HTN unopposed estrogen therapy asbestos exposure petroleum products heavy metals chronic renal failure acquired cystic disease (dialysis) tuberous sclerosis
pediatric renal tumor
presents age 2-5 yr with most by age 10
WAGR syndrome: Aniridia, Genital abnormalities, mental Retardation
WT1 deletion is “first hit” but tumor develops after second hit
Morph: tightly-packed blue cells (blasts)
Presentation: hematuria, pain in abdomen after trauma, HTN
Wilms tumor
Denys-Drash -> gonadal dysgenesis associated with WT1 mutation
vesical inflammatory reaction related to chronic bacterial infection with E coli or Proteus
most common in transplant patients (immunosuppression)
macrophages stuffed with particulate and membranous debris of bacterial origin
Malacoplakia
occurs more frequently in countries with urinary schistosomiasis
nearly always associated with chronic bladder irritation and infection
squamous cells carcinoma of the bladder
risk factors for adenocarcinoma of the bladder
cigarette smoking industrial exposure to arylamines schistosoma haematobium infection long-term use of analgesics cyclophosphamide bladder irradiation
benign sexually transmitted tumor caused by HPV 6 & 11
related to the common wart
Condyloma acuminatum
50% are from HPV (esp 16 and 18)
-cigarette smoking increases risk
squamous cell carcinoma of the penis
Where do most adenocarcinomas of the prostate arise?
70% arise in the peripheral zone in a posterior location where it may be palpable on rectal exam
What part of the kidney do lymphatics drain?
Lymphatics drain the interstitial fluid of the cortex. They may contain high concentrations of EPO. Lymphatics do not drain the medulla, because that would impair the ability to concentrate urine.
Describe the mesangial cells
They comprise a network of contractile cells which secrete EC matrix. The network is continuous with the smooth muscle cells of the afferent arteriole, efferent arteriole and extend to the extraglomerular mesangial cells which are part of the JGA.
specialized smooth muscle cells that produce, store and release renin
granular cells
Features of the cells of the TAL
tall interdigitations and numerous mitochondria within extensively invaginated basolateral membrane. The TAL terminates at the macula densa.
Included in the distal tubule
macula densa, connecting tubule, initial collecting tubule. Early distal tubule = DCT; late distal tubule = initial collecting tubule
Where is the first location of intercalated cells?
connecting tubule. The connecting tubule has connecting tubule cells and intercalated cells.
What do connecting tubule cells release?
kallikrein
Are the cells of the Initial collecting tubule and the cortical collecting tubule identical?
Yes. They are composed of intercalated and principal cells.
What do alpha-intercalated cells secrete?
They secrete H+ and absorb K+
What do principal cells absorb?
Principal cells absorb NaCl and secrete K+
