Back to: Renal-Urinary Systems
Obstructive Renal Conditions
Renal Stones (Nephrolithiasis)
This is the presence of a stone which can get lodged somewhere in the urinary tract.
It usually in one of the 3 natural points of constriction – pelviureteric junction (PUJ), pelvic brim or vesicoureteric junction (VUJ).
There are different types of stones
Types of Kidney Stones
Calcium oxalate/phosphate
These are the most common type, which occur due to hypercalciuria.
They can be due to loop diuretics, steroids, acetazolamide and theophylline.
Hydrochlorothiazide (calcium-sparing diuretic) can be used to prevent these stones
Struvite (Magnesium Ammonium Phosphate)
This type is often seen due to infection with a urease-positive organism.
It alkalinises the urine causing formation of alkaline stones and staghorn calculi.
Uric Acid
These stones occur when the urinary pH is low causing uric acid to precipitate.
There is an increased risk in gout and malignancy (uric acid release).
They can also occur secondary to an ileostomy, as the loss of HCO3 – ions makes the urine more acidic, so uric acid crystals are more likely to form.
Cysteine
This is seen in children with genetic disorders e.g. cystinuria (autosomal recessive)
Risk Factors
Dehydration – this increases ion concentration of the urine
Recurrent UTIs and foreign bodies which stagnate flow, e.g., stents/catheters
Diet – may cause hypercalcaemia and certain foods also increase oxalate levels
Underlying metabolic conditions (e.g., hyperparathyroidism)
Symptoms
Writhing (colicky) pain which travels from “loin” to groin with nausea/vomiting
Painful haematuria and proteinuria and sterile pyuria
If left untreated, increases the chance of a secondary UTI
Key tests
Non-contrast CT is the investigation of choice
Management
Analgesia, e.g., intramuscular/PR diclofenac for rapid relief of pain
Stones < 5 mm usually pass spontaneously, so can be managed conservatively
Stones > 5 mm are unlikely to pass spontaneously. Here, options include shockwave lithotripsy, uteroscopy and percutaneous nephrolithotomy
Renal Artery Stenosis
This term refers to narrowing of the renal arteries, impairing renal blood flow.
Poor renal blood flow then causes activation of the renin-angiotensin system to reabsorb water.
This leads to renin release which can lead to profound hypertension.
Causes
Atherosclerosis – this develops over a period of time
Fibromuscular dysplasia – this is a non-inflammatory condition that leads to protrusions in the artery walls interrupting blood flow, seen in young females
In transplanted kidneys, transplant renal artery stenosis (TRAS) can be a sign of immune rejection of the graft kidney
Symptoms
Treatment resistant hypertension
Can lead to acute decompensated heart failure resulting in pulmonary oedema
Secondary hyperaldosteronism (high BP, hypokalaemia, and metabolic alkalosis)
Key tests
Doppler ultrasound – shows renal artery flow
Magnetic resonance angiogram (MRA) shows narrowing of the renal artery
Management
Management of cardiovascular risk factors.
If due to transplant rejection, this will require specialist management involving immunosuppression.
