Renal Flashcards
Obstructive uropathy - causes?
Kidney - calculus, chronic infection granulomatous, neoplasm, necrotising papillitis
Ureter - stricture, stenosis, kinks, chronic infection, congenital valve, retrocaval ureter, neoplasm, calculus, compression (nodes, tumour, abscess, haematoma), ureteritis cystica, ovarian vein syndrome, trauma
Bladder - ureterocele, neoplasm, diverticulum, calculus, foreign body, congenital neck obstruction, schistosomiasis,
Urethra - neoplasm, stricture, diverticulum, papilloma, meatal stenosis, BPH (men), prostatitis (men), prostate Ca (men), strangulation (men), phimosis (men)
Presentation of renal colic
Loin to groin pain
Types of renal calculi?
75% Ca Oxalate (phosphate)
15% Mg ammonium phosphate
10% uric acid or cysteine
Risk factors for renal calculi?
Concentrated urine, hereditary, diet, co-morbidities (sarcoidosis, inflammatory bowel disease, cancer)
Common sites of obstuction of ureter by kidney stone?
- Ureterovesical junction
- Crossing of iliac artery (mid ureter)
- Ureteropelvic junction
Possible routes of kidney infection?
Haematogenous vs Ascending
Predisposing factors in acute pyelonephritits
Anomalies of kidney or ureter, calculi, obstruction at any level, DM, pregnancy, neurogenic bladder, instrumentation
Clinical features of acute pyelonephritis
Bacteriuria (>100000/ml3)
Proteinuria absent or minimal
White cell casts and leukocytes
F>M
Tenderness at costovertebral angle
Tenesmus, pain/burning on urination
? Haemodynamic compromise
Renal fusion types
- Crossed ectopia with fusion.
- S shaped sigmoid hidney
- Pelvic cake/lump kidney
- Horseshoe kidney - developing kidneys fuse usually with lower lobes, anterior to aorta, lies low in abdomen,. Most common fusion.
Fused kidneys are close to midline, have multiple renal arteries and are malrotated. Obstruction, stone formation and infection are potential complications.
Wilm’s tumour
Nephroblastoma, characterisctic variegated structure with pseudocapsule. Almost exclusive to infants. Mass in loin/abdomen (ddx single cyst/PKD, large hydronephrosis, neuroblastoma).
Loss of weight, anaemia, haematuria, HTN
Mets late but LN, lungs, liver
In contrast to neuroblastoma where bone mets +++
Surgical approach to the kidney
Lumbar - extraperitoneal, non muscle-splitting vertical incision on lateral back. For removing pelvic and upper urethral stones.
Lateral (flank) - extraperitoneal, patient positioned in lateral flexed position. For retrieving renal stones. Stressed skeleton and resp system as pt is in uncomfortable position
Anterior - midline, paramedian (extraperitoneal or transperitoneal), chevron
Embryology - development of the urinary system
Initially intermediate mesoderm differentiates into nephrogenic tissue and forms a pronephros (doesn’t work and degenerates) and mesonephros (functions briefly) retroperitoneally. Definitive kidney develops from metanephric tissue into which ureteric bud grows and differentiates into renal pelvis, calyces and collecting duct.
Kidneys ascend from deep in the pelvis to posterior abdominal wall (always retroperitoneal). Hilum faces anterioly at first, but rotates 90* so that renal pelvis faces medially and renal vessels connect at the hilum
Definition: Renal Hilus
Medial aspect of kidney containing the entrance to renal artery, vein and the renal pelvis
Gross kidney anatomy - relation to outside
Stretch from T12 - L3
Right K lower then L because of liver
Kidney –> Fibrous capsule –> Perinephric fat –> Perinephric/Perirenal fascia (also encloses andrenal gland)
Renal cortex - outer bit which contains all glomeruli and medulla contains loops of hence, vasa recta and final collecting ducts
Innervation of the bladder
S3 S4 S5
Cortical vs Juxtamedullary Nephrons
Cortical nephrons occur throughout renal cortex and have short loops of hence
JM nephrons begin need corticomedullary junction and have long loops of hence descending deep into medulla which can highly concentrate urine.
Cortical > JM 7:1
In which cell is EPO made?
Fibroblast-like interstitial cells of the kidney
What is the role of mesangial cells in the glomerulus?
Provide a scaffold to support the many capillaries in Bowman’s capsule. Have contractile and phagocytic properties
What are the 3 components of the glomerular filtration barrier?
- Endothelial cells - thin with 70nm pores filled with -ve charges podocalyxin
- GBM - specialised capillary basement membrane. 2 layers made up of type IV collagen, fibronectin, heparin sulphate proteoglycans, lamina, podocalyxin. TIV collage forms helical strands arranged into 3d framework to which everything else is attached.
- Epithelial cells of Bowman’s capsule (podocytes) - long projections with foot processes which attach to GBM. Foot processes form mesh with filtration slits of 25-65 nm. Key selective barrier preventing passage of large molecules
Renal Hx and Examination
Esp –> Drugs, FHx, Infection, PMHx
Urine appearance
Exam –> Abdo/Cardiac. (Note BP, JVP, Fundoscopy, Renal bruit, oedema)
Urine microscopy - casts
Microscope with phase contrast to examine fresh urine. Centrifuge if possible .
RBC - Can arise from anywhere in tract but deformed (dysmorphic) indicates glomerular bleeding (glomerulonephritis)
RBC casts - glomerulonephritis
WC - inflammation. Polymorphonuclear cells - infection. Eosinophils/lymphocytes - interstitial nephritis
WC casts - acute bacterial infection
Waxy casts - large, occur in dilated tubules in CRF
Hyaline casts - normal
Granular casts - normal
Crystals - variable significance as can form after collection. Ideally ASAP >37*C
At what eGFR level do you expect urea and creatinine to rise?
About 30mL/min
Why does creatinine clearance slightly overestimate GFR?
GFR (vol of filtrate formed in 1 minute) estimated by measuring plasma and urine concentration of a substance and the urine flow rate per minute.
Tubular creatinine secretion overestimates GFR when creatinine clearance is used to estimate GFR
Inulin is better, as is very inert, but only used for research purposes.
eGFR often estimated with algorithms using plasma Cr, age, weight, gender
Renal anti-immune profile
ANCA - vasculitis
Anti-GMB Goodpasture’s
ANA/anti ds-DNA, low complement levels - SLE
What is the approach for renal biopsy?
Percutaneous biopsy performed with long cutting needle through back under US guidance. Tissue examined by light microscopy, immunostaining, electron microscopy
Causes of ARF (in %), mortality, prognosis
Pre-renal, inadequate perfusion (50-65% cases)
Renal, intrinsic renal disease (20-35% cases)
Post-renal, obstructive (15% cases)
Overall mortality 30-70%
Prognosis –> 60% regain normal renal function, 15-30% have impairment, 5-10% ESRF
What is the pathophysiology of ATN?
Most AKI results from ATN, usually 2* to renal hypo perfusion, often in the context of sepsis / nephrotoxic drugs
1. Renal ischaemia causes swelling of tubules
2. Tubular cell death and shedding into lumen causes blockage, raising tubular pressure, stopping glomerular filtration.
3. Swollen tubules compress nearby vasa recta, further reducing perfusion
Ischaemia alos results in production of free radicals which further damage cells and mitochondria, used up ATP means Ca cannot be explode from cells, and high IC Ca interferes with cell metabolism.
Apoptosis and necrosis of tubular cells are common
Pre-renal causes of ARF
Inadequate cardiac function, circulatory volume depletion, obstruction of arterial blood supply. Resulting renal ischaemia causes ATN
Name 10 nephrotoxic agents
Aminoglycosides - tubular toxin
NSAIDs - inhibit Pg mediated vasodilation
ACEi/ARB - reduce efferent arteriole tone
Cephalosporins - tubular toxin
Amphotericin B - vasoconstriction and membrane damage
Aciclovir/Indinavir - precipitate in tubules
Ciclosporin/Tacrolimus - indirect vasoconstriction
Radiocontrast - vasoconstriction
PPIs - allergic tubulointerstitial nephritis
RIFLE criteria for ARF
Classification of severity of ARF looking at serum Cr and UO. To be used after optimal state of hydration achieved and easily reversible causes (obstruction) excluded
RISK - Cr increase x1.5 baseline OR UO <0.5mL/kg/h >6hours
INJURY - Cr increase x2 baseline OR UO <0.5mL/kg/h >12h
FAILURE - Cr increase x3 baseline OR UO <0.3mL/kg/h x24h or anuria >12h
LOSS - persistent failure >4 weeks
ESRD
Correlates well with length of stay in ICU, hospital, mortality, renal recovery
Name some tubular toxins
Heavy metals
Contrast media
Haemoglobin
Myoglobin
How does acute hypercalcaemia cause AFR?
Renal vasoconstriction and calcium phosphate precipitation in tubules
How does myeloma cause ARF?
Light chain precipitation in tubules can cause case nephropathy and AKI