Session 7 Flashcards
What are calcium renal stones composed of?
Most are calcium oxalate and calcium phosphate but may just be calcium phosphate, or uric acid.
Why do struvite renal stones form?
Due to presence of bacteria with urease enzymes, cause formation of stones containing urease or triple-phosphate.
When do cysteine renal stones form?
In cysteinuria.
What drugs can cause renal stones to form?
Indinavir, trimterene or sulphadiazine.
Why do renal stones form?
Urine becomes supersaturated with minerals; seed crystals form via nucleation; mineral deposits form around the seed crystal and the stone grows.
What are Randall’s plaques?
Calcium plaques present on the membranes in the urinary tract; very easy for renal stones to form around these plaques.
What factors increase the likelihood of renal stone formation?
Urine stasis, drug use, genetic/congenital disorders.
What conditions are calcium oxalate stones associated with?
Conditions causing hypercalcaemia, hyperoxaluria and hypercalciuria, e.g. Hyperparathyroidism , diffuse bone disease, sarcoidosis, Crohn’s disease, etc.
What effect does PTH have on calcium homeostasis?
Increases serum calcium by increasing osteoclastic bone resorption; increasing intestinal calcium absorption; increasing calcitrol synthesis; increasing phosphate secretion.
What effect does vitamin D have on calcium homeostasis?
Increases serum calcium by increasing calcium gut resorption; increasing calcification and resorption of bone.
What effect does calcitonin have on calcium homeostasis?
Decreases serum calcium by inhibiting osteoclastic bone resorption; increasing renal excretion of calcium and phosphate.
What commonly causes hypercalciuria?
Idiopathic, hypercalcaemia, excessive dietary calcium intake, excessive resorption of calcium from the skeleton due to weightlessness or immobilisation.
How is hypercalcaemia commonly caused?
Hypersecretion of PTH; destruction of bone tissue; other mechanisms such as sarcoidosis, thiazide diuretics, excessive vit D ingestion, milk-alkali syndrome.
What are the common symptoms of hypercalcaemia?
Bones, stones, grooms and moans: painful and easily fractured bones, renal stones, abdominal groans, psychic moans.
How is hyperoxaluria usually caused?
Autosomal recessive disorder in oxalate synthesis (primary hyperoxaluria); increased intestinal oxalate absorption secondary to GI disease (Crohn’s disease, etc.); high dietary oxalate intake; low calcium intake.
What is hyperuricaemia?
Excess uric acid in the blood.
What does hyperuricaemia predispose patients to?
Uric acid stones.
What usually causes hyperuricaemia?
Increased cell turnover: due to lympho- or myelo-proliferation disorders or after chemotherapy due to tumour lysis syndrome.
How do renal stones usually present?
Usually asymptomatic but may have colic, dull loin aches, recurrent UTIs, haematuria, renal failure or UT obstruction.
How does colicy pain usually present?
Very painful bouts lasting 20-60 minutes caused by peristaltic contractions or spasm of the ureter radiating from the flank to iliac fossa and testes/labium/inner thigh in the L1 nerve root. May be accompanied by nausea, vomiting, pallor, sweating and restlessness.
How are renal stones investigated?
MSU, RBCs, urinary casts, urinary crystals, urine cultures, serum levels (urea, creatinine, electrolytes and calcium), CT best investigation as sees most stones.
What are common complications of renal stones?
Acute pyelonephritis, gram-negative sepsis, necrosis of the renal parenchyma, urinary obstruction, hydronephrosis, ulceration through the collecting system walls.
How are renal stones treated?
Analgaesia and warmth to site of pain; bed rest; ureteroscopy; pericutaneous nephrolithotomy; ESWL therapy.
How can renal stones be prevented?
Drink more to decrease urine supersaturation; alkalinity urine with potassium citrate.
What types of bacteria usually cause UTIs?
Coliforms and gram-negative rods.
What host factors can increase likelihood of a UTI?
Shorter urethra (women); urethral obstruction due to enlarged prostate, pregnancy, stones and tumours; neurological problems causing incomplete emptying of the bladder and residual urine; ureteric reflux causing ascending infection of the bladder.
Why does UTI typically occur in the pelvic-ureteric junction?
Due to stones.
Why does UTI typically occur in the ureter?
Due to calculus, cancers or retroperitoneal fibrosis.
Why does UTI typically occur in the bladder?
Due to nephrogenic bladder.
Why does UTI typically occur in the vesicoureteric junction of the bladder?
Due to stones.
Why does UTI typically occur at the bladder neck?
Due to hypertrophy.
Why does UTI typically occur in the prostatic urethra?
Due to cancer or benign prostate enlargement.
Why does UTI typically occur in the urethra?
Due to stones.
What bacterial factors increase likelihood of UTI?
Fimbrae, haemolysin secretion, K antigen, urease secretion.
How does cystitis usually present?
Lower UTI: pain and burning on urination, high frequency and urgency to urinate, dysuria, low grade fever.
How does acute pyelonephritis usually present?
Fever, loin pain (often one sided and localised to kidney), dysuria, increased frequency of urination.
What is an uncomplicated UTI?
Infection by a usual organism in a patient with a normal urinary tract and normal urinary function.
What is a complicated UTI?
UTI when one or more factors are present to predispose the person to persistent infection, recurrent infection or treatment failure.
In which patient groups is a UTI usually complicated?
Men, children, pregnant women, pyelonephritis sufferers, recurrent infection sufferers, patients with failure of treatment, patients with other complications.
When should and shouldn’t a urine culture be performed when investigating a UTI?
Perform if complicated UTI is suspected, don’t perform if uncomplicated.
How are urine specimens taken when screening for UTI?
Usually MSU, can also take catheter sample or suprapubic aspiration. Transported to lab at 4 degrees in boric acid.
What does turbid urine suggest?
Presence of UTI.
When is dipstick testing useful in UTI screening?
To exclude UTI in children, men and elderly women.
When is dipstick testing not useful in UTI screening?
Acute uncomplicated UTIs in women; men with typical/severe symptoms; catheterised patients; older patients without features of infection.
What is microscopy likely to show in patients suffering from UTIs?
Presence of WBCs and RBCs as well as squame cells.
When should imaging be used in investigating a suspected UTI>
Always in children, also useful in septic patients to establish renal involvement.
How should asymptomatic bacteriuria be treated?
Shouldn’t be treated usually as doesn’t increase mortality, treat like UTI in pregnancy or urological surgery.
How are UTIs treated?
Increase fluid intake; address underlying cause; give antibiotic course: 3 days for uncomplicated, 5-7 days for lower complicated UTI; only treat catheter patients if systemically unwell; give prophylaxis if recurrent UTIs.
What antibiotics are prescribed in simple cystitis infections?
Trimethoprim or nitrofurantoin.
Why is a short course of antibiotics given in simple cystitis?
5-7 day course is no more effective and shorter course reduces selection pressure for resistance.
What antibiotics are given in complicated lower UTIs?
Trimethoprim, nitrofurantoin or cephalexin.
How is pyelonephritis treated?
14 day course of coamoxiclav, ciprofloxacin or gentamicin.
Why isn’t nitrofurantoin used in pyelonephritis?
Has systemic activity.
Should all symptomatic adult women be given treatment for UTI?
No. Most infections are self limiting so don’t need antibiotic treatment.
