Renal Tubule Disorders

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

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.