Figure 5.13. retrograde ureterogram in a patient with severe hydronephrosis and macroscopic hematuria. multiple irregular filling defects are identified throughout the ureter indicating extensive ureteric tcc.

Renal Mass Biopsy

If there is uncertainty about the nature of a renal mass, percutaneous image-guided biopsy can be performed. Image-guided renal biopsy can be performed under ultrasound, which allows the biopsy needle to be viewed in real time (Fig.5.14), or under CT guidance. The sensitivity of biopsy for the diagnosis of malignancy is about 80–90%.8

Renal Stone Disease

Renal calculi are relatively common with an approximate incidence of 10% in the adult population. Recurrent urinary tract infections, renal structural anomalies (Table 5.3), such as medullary sponge kidney (Fig. 5.15), hypercalciuric states and urinary stasis predispose to an increased risk of stone formation.

Renal calculi are often detected in patients undergoing investigations for hematuria or urinary tract infections. Clinically, silent calculi may be detected incidentally during imaging tests for other reasons. Acute ureteric colic is a frequent presentation in patients with renal calculi. Although small calculi usually pass spontaneously, occlusive ureteric calculi left untreated may lead to obstructive nephropathy. Occasionally, obstructing ureteric calculi can lead to

Table 5.3. Upper tract structural abnormalities predisposing to stone formation

medullary sponge kidney calyceal diverticulum Pelvi-ureteric junction obstruction horseshoe kidney

Control INSP

Figure 5.15. medullary sponge kidney.an autosomal dominant condition in which calcifications develop within dilated ectatic renal collecting ducts. a characteristic appearance is seen on plain radiographs with multiple renal calculi distributed throughout the medulla.

life-threatening urosepsis. Accurate imaging is therefore essential for appropriate management.

Renal calculi can be imaged by plain radiographs, IVU, ultrasound, or CT. MRI, due to its inability to visualize calcified structures has no clearly defined role in the imaging of renal calculi.

Ultrasound

Renal calculi are often be detectable by ultrasound however visualisation of calculi can be inconsistent and unreliable.9 Typically, renal calculi are seen as echogenic foci situated in the renal medulla with associated acoustic shadowing (Fig. 5.16).

In acute renal colic, ultrasound may demonstrate features indicating renal obstruction. This is usually suggested by the presence of hydronephrosis. Visualization of ureteric calculi is

Figure 5.16. Ultrasound image demonstrating a calculus in the lower pole of left kidney (arrow) with associated acoustic shadowing.

often problematic as the ureter is often obscured by overlying bowel gas. However, it may be possible to detect calculi at the pelviureteric junction or at the vesico ureteric junction.

Plain Radiographs and IVU

Plain radiographs have a sensitivity of 60% for renal calculus detection and are useful for the follow-up of patients with known radio-opaque calculi (Fig. 5.17). Combined with IVU, they can provide useful information about stone size, configuration, and anatomical position.

Calcium oxalate, calcium phosphate, and cysteine stones are generally visible on plain radiographs, whilst stones composed of uric acid, xanthine, and matrix material are radiolucent.

In acute renal colic, IVU usually demonstrates delayed contrast excretion from the affected kidney with associated hydronephrosis and hydroureter (Fig. 5.18). IVU for ureteric colic has in many centers been replaced by the use of CT-KUB.

CT

Non-contrast CT (NCCT) is the imaging test of choice for detection of renal calculi. With a sensitivity of over 98%, it has in many centers become established as the first-line test for patients with suspected renal colic. CT for ureteric colic does not require the use of intravenous contrast medium, thus avoiding the