The most common urinary tract infections are bacterial in origin, with viral and fungal infections being comparatively rare. The diagnosis is made by
urinalysis after the patient presents with symptoms of dysuria, haematuria and/or suprapubic or renal angle pain. The origin of the infection may be via
the blood stream (haematogenous) or the urethra (ascending). Ascending infections are more common in women due to their short urethra.
Ultrasound is often requested, particularly in children, to identify any unsuspected renal pathology which may be associated with the infection,
for example a duplex collecting system, pelvic kidney.
Common conditions which may be identified on ultrasound include renal cystic diseases, calculi, obstructive uropathy, reflux and anatomical variants.
The infection may be either acute or chronic. Ultrasound signs of renal infection may be absent altogether, and this is the commonest scenario as
the infective episode has often been successfully treated with antibiotics by the time the ultrasound scan is performed.
The infection may be confined to the bladder, that is cystitis, in which case low-level echoes and/or hyperechoic debris may be identified, or may have
progressed to the kidneys. Scarring and/or cortical thinning may be present in cases of repeated infections.