Unwanted surprise during preoperative imaging for a staghorn calculus

A male patient of 63 years-old, with diabetes mellitus, arterial hypertension and dyslipidaemia. He had recurrent symptoms of stone disease over the last 15 years, and had no previous episodes of acute pyelonephritis or haematuria.

An X-ray abdomen and pelvis (KUB) was initially obtained, and showed bilateral renal stones, with fragmented staghorn morphology on the right kidney (Fig. 1). A renal ultrasound was performed and detected additional anomalous calyceal anatomy of the right kidney, with a calyceal diverticulum (Fig. 2).

CT was performed for surgical planning, and a complete uro-CT protocol was acquired for calyceal anatomy definition. It confirmed bilateral urolithiasis with a staghorn calculus in the right kidney, occupying the renal pelvis and various calyces and showing fragmentation, and density values higher than 1000 Hounsfield units (Fig. 2). The presence of a right lower pole calyceal diverticulum was noted. A solid mass with heterogeneous contrast-enhancement was identified in the superior calyces and renal pelvis, with focal invasion of the renal cortex and involving the staghorn calculi (Fig. 3). No further lesions were identified in the excretory system, with normal contrast filling of both ureters and bladder during the excretory phase.

Urolithiasis is a frequent urologic disease with high social impact and MDCT is the gold-standard method for diagnosis and follow-up. It is a useful tool for surgical planning, particularly since percutaneous nephrolithotomy (NLPC) is now considered the preferred treatment when stone burden is high and/or staghorn morphology is present. This method gives the most information about the calculus and pre-contrast acquisition can be sufficient in many cases [1]. It gives an accurate stone burden estimation using stone size or volume [2] and other morphometric data can be retrieved for staghorn calculi with complex 3D morphology [3,4]. Calculus composition can be obtained either using HU values or more accurately using dual-energy CT technology [5]. The use of intravenous contrast is not consensual for treatment planning, but it can be useful for accurate definition of the calyceal anatomy or to clarify anomalous findings in the pre-contrast study. In this case, we report a concomitant tumour in the excretory system detected during surgical planning, highlighting the additional benefit of this technique for its ability to reveal urinary abnormalities with great clinical relevance [1].

Transitional cell carcinoma (TCC) accounts for up to 10% of neoplasms of the upper urinary tract [6] and it represents a low percentage of urothelial tumours, which mostly originate from the bladder. These are typically tumours of older patients, with a male predilection, and usually present with haematuria, or even with renal colic when there is obstruction of the urinary system, which might cause difficulties for its clinical differential diagnosis with renal stones. In addition, renal cell carcinoma is a more frequent tumour which is particularly important to discard. In contrast to the latter, TCC is centred to the excretory system and usually does not distort the renal outline, even in cases such as this, with renal parenchyma invasion.

MDCT is the best exam for diagnosis, staging, and post-operative follow-up, and an optimised protocol is very important [7]. Staging according to the TNM-system has important prognostic implications for the development of local recurrence and metastases, affecting overall survival. Moreover, MDCT helps in the exclusion of multicentric diseases which is quite common in TCC, making the assessment of the entire urothelium essential before treatment, including the use of cystoscopy. MRI is increasingly used as an alternative or complementary imaging of TC [8], and it might be particularly useful when the patient has contraindication for intravenous contrast administration or when malignancy is not certain.

Although percutaneous resection might be a choice for smaller lesions, in locally advanced tumours such as our case (which was a stage III tumour: T3N0M0), nephroureterectomy is the treatment of choice. Moreover, a careful follow-up should be done to detect disease recurrence [6,7].

Written informed patient consent for publication has been obtained.