Renal Flashcards by Eliot Carrington-windo

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Describe mechanism of TURP syndrome

-Irrigation fluid for TURP is hypo-osmolar
-Hyposmolar solution used to avoid diathermy injury to pt from resectoscope
-If absorbed via prostatic venous sinuses: can result in hyponatraemia and hypervolaemia

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Why does TURP syndrome cause change in bp?

Volume overload initially causes hypertension
Subsequently causes cardiac insufficiency and hypotension

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What is TURP syndrome?

-Caused by absorbtion of large amounts of irrigation fluid into prostatic venous sinuses
-Syndrome can be caused by hyponatraemia (<125mmol/L) or hyperammonaemia (metabolite of glycine)

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What are signs and symptoms of TURP syndrome?

-Hypertension and then hypotension
-Tachycardia
-Hypoxia (overload)
-Dyspnoea (overload)
-neurological: confusion, disorientation, convulsions, coma

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What is the mechanism behind neurological symptoms in TURP syndrome?

Hyponatreamia causes osmotic gradient in the brain resulting in cerebral oedema and raised ICP

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What are the most appropriate irrigation fluids for use in TURP syndrome?

Hypoosmar solutes (Glycine, Sorbitol, Manitol)

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How would you manage hypotensive patient with TURP syndrome?

Resuscitate according to Ccrisp protocol
Identify bleeding, take bloods including osmolality
Stop IVI
Inform ITU/HDU and operating surgeon

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Where should hypotensive pt with TURP syndrome be managed?

in ITU/HDU
Risk of developing cerebral/pulmonary oedema

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What precautions can be taken to minimise risk of TURP?

Minimise operating time
Close monitoring of observations during surgery
Keep fluid bag low to reduce pressure
Minimise operative bleeding

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How is hyponatraemia classified?

Hypervolaemic: Excess water dilutes sodium
Euvolaemic: Hyponatraemia in presence of normal water levels
Hypovolaemic: water and sodium levels are both low

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What are causes of hypervolaemic hyponatraemia?

Renal failure, liver failure, heart faliure, iatrogenic fluid overload

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What are causes of euvolaemic hyponatraemia?

SIADH
Hypothyroidism

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What are causes of SIADH?

-CNS causes: mass/bleed (trauma, sah), infection (meningitis)
-Pulmonary causes (pneumonia, asthma
-Cancer: gi, lung, genitourinary
-Drugs: (SSRI)

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What are causes of hypovolaemic hyponatraemia?

-Marked blood loss
-Inadequate replacement of fluid and electrolytes
-sepsis

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How is sodium reabsorbed by the kidneys?

Majory (60%) of filtered sodium is reabsorbed in the PCT via an ATP dependent pump
-20% loop of henle: passive due to countercurrent mechanism
-remainder dct and collecting ducts under control of aldosterone (active)

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What is absorbed in proximal convoluted tubule?

Sodium reabsorption (60%) via ATP dependent pump
Passive reabsorption of chloride ions
Water reabsorption down osmotic gradient

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What is absorbed in loop of henle?

Loop of henle reabsorbs 25% filtered sodium
Passive reabsorption of chloride ions
Ascending limb impermeable to water
Reabsorption of water in descending limb down osmotic gradient

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What is absorbed in loop of henle?

Sodium reabsorption (25%)
Passive reabsorption of chloride ions
Ascending limb impermeable to water
Loop of henle reabsorbs 25% of filtered sodium

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What is absorbed in distal convoluted tubule?

-Sodium reabsorption (8%). This process is energy dependent.
-Reabsorption of sodium in dct and collecting duct is partially under control of aldosterone
-Low osmolality of ultrafiltrate entering dct leads to passive reabsorption of water, which continues in collecting ducts

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Explain the countercurrent mechanism

-formed by two parallel limbs in loop of henle
-Ascending limb is highly impermeable to water but permeable to solutes (Na, Cl)
-Reabsorption of solutes creates osmotic gradient in medullary interstitium and raises osmolality of this compartment
-Leads to reabsorption of water from descending limb

Define acute renal failure

Sudden impairment of the kidney’s ability to excrete nigtrogenous waste products of metabolism

Causes of pre-renal failure

Dehydration
Sepsis
Heart failure
Blood loss

Causes renal AKI

-ATN
-Glomerulonephritis
-Hepatorenal syndrome
-Vasculitis
-Nephrotoxic medications

Causes Post renal AKI

Obstruction from calculi Prostatic obstruction (BPH, Cancer) Renal/bladder tumour Extrinsic compression from pelvic tumours

What is the pathogenesis of acute renal failure?

-reduced perfusion pressure -> efferent vasoconstriction -> reduced blood flow and cortical/medullary ischaemia -> shedding cells into lumen -> back leak fluid into insterstitium -> increased medullary hydrostatic pressure—> reduced re absorption renal parenchyma ischaemia results from fall in perfusion pressure -This leads to vasoconstriction of efferent arterioles which preserves capillary filtration pressure -Contricted efferent arterioles have reduced blood flow, resulting in worsening cortical and medullary ischaemia -Ischaemic cells are shed into tubular lumen causing obstruction, which promotes a 'back leak' of tubular fluid into interstitium -This raises interstitial hydrostatic pressure, which reduces tubular fluid reabsorption and worsens oliguria

Which part of nephron will be affected by acute renal failure first?

-thick ascending limb—> within medulla, most atp pumps Cells of thick ascending limb are most susceptible to ischaemic injury -This is because they are within medulla, which has poorer oxygenation than cortex -Also, active ATP pumps at cell membrane have higher oxygen demand

Where is renin released from in kidneys and what triggers its release?

-Renin is released from juxtaglomerular apparatus Renin release is triggered by: -Reduced renal perfusion -Sympathetic nervous system stimulation -Catecholamine release -Hyponatraemia Renin cleaves angiotensin 1 from angiotensinogen

Name some nephrotoxic drugs

NSAIDS ACE inhibitors Gentamicin Furosemide Thiazide diuretics

Name some important life-threatening complications of acute renal failure

-Fluid retention and hypervolaemia leading to acute pulmonary oedema -Hyperkalaemia leading to metabolic acidosis and cardiac arrythmias

How would you manage hypperkalaemia?

10ml 10% calcium gluconate Insulin dextrose infusion Salbutamol Calcium resonium Treat cause

What are the indications for renal replacement therapy?

Acidosis Refractory hyperkalaemia Refractory pulmonary oedema and fluid overload Uraemic encephalopathy Removal of toxins

Grade 1 kidney injury

Renal contusion, non-expanding subcapsular haematoma

Grade 2 kidney injury

Laceration <1cm in depth not involving renal medulla and collecting system, non-expanding retroperitoneal haematoma

grade 3 kidney injury

Laceration >1cm not involving collecting system

grade 4 kidney injury

Laceration >1cm extending into collecting system, renal vessel injury with haemorrhage

Grade 5 kidney injury

Shattered kidney or avulsed renal vessels

What are the indications for surgical management of renal trauma?

Haemodynamically unstable patient indicating ongoing bleeding Expanding perinephric haematoma Avulsion of renal pedical

When would you suspect urethral injury in a patient?

-Bleeding from urethra -Perineal haematoma -Scrotal haematoma -High riding prostate on DRE in male

What is the likely anatomical site of urethral injury in a male in pelvic ring fractures and in 'saddle injuries'?

Pelvic ring fractures: membranous part of urethra -Saddle injuries: bulbar urethra

What investigation would you do to confirm urethral injuries?

Retrograde urethrogram

How woulld you manage a patient with suspected urethral injury?

If there is no extravasation on retrograde urethrogram, urinary catheter If there is extravasation, suprapubic Formal surgical repair can be considered at later stage.

What investigations would you perform for renal acolic?

Bloods: U + E, Bone profile, urate Imaging: CTKUB, US if pregnant

What are the common sites of stone impaction along the ureter?

-Pelvi-ureteric junction -When the ureter crosses pelvic brim -Vesico-ureteric junction

What are the different types of renal stones?

Calcium oxalate stones Calcium phosphate stones Struvite stone: magnesium and ammonia (also known as infection stone) Uric acid stone

What is a staghorn calculus?

Stone occupying renal pelvis and at least one calyceal system

Which stones can you manage conservatively?

Stones <4mm will almost always pass spontaenoiusly

How would you manage pt with a stone >1cm and impaired renal function?

-Ureteric stent placement -Percutaneous nephrostomy

How would you manage renal stones?

-Conservative management -Ureteroscopy and stone retrieval -ESWL -Percutaneous nephrolithotomy

What are the causes of haematuria?

Infection: -Cystitis -Prostatitis Autoimmune -Glomerulonephritis -Iga nephropathy Tumours Renal stones Trauma

What investigations would you consider in pt with haematuria?

-Bloods -Renal US -Flexible cystoscopy -CT urogram

What are the different types of renal tumours?

Benign -Adenoma -Angiomyolipoma -Cysts Malignant -Wilm's tumour -RCC -TCC