Surgeons Remove Kidney Stones Without Contrast Guidance in Selected Patients

In a retrospective cohort of 57 patients treated at a tertiary hospital between 2025 and 2026, a technique called stone-guided percutaneous nephrolithotomy, or sg-PCNL, achieved a stone-free rate of 94.6 percent, with all procedures performed by a single surgeon relying on the stone itself as the target. The study, published in the African Journal of Urology, suggests that in select cases the conventional first step of threading a retrograde ureteral catheter and opacifying the pelvicalyceal system with contrast may be omitted without compromising safety.

Percutaneous nephrolithotomy is the preferred operation for large kidney stones because it delivers high stone-free rates. In the conventional approach, a catheter is passed retrograde up the ureter so that contrast dye can outline the pelvicalyceal system, the branching collecting structure of the kidney, under fluoroscopy. That roadmap helps the surgeon puncture the correct calyx, one of the cup-shaped extensions of the collecting system, with a needle. Variations exist, including ultrasound-guided, fluoroscopy-guided, and combined techniques, but puncturing solely under fluoroscopy with no contrast and no ultrasound has been considered unreliable, with limited evidence on its safety.

The new technique turns the stone into its own landmark. The surgeon aims the initial puncture needle at the distal margin of a calyceal stone, targets it end-on using the Bull’s eye technique, and aligns the needle along the stone’s long axis, all under continuous fluoroscopic guidance. The needle is advanced in one- to two-centimetre increments, and needle depth is confirmed by rotating the C-arm to a vertical orientation. Correct positioning is verified not by aspirating urine, which the authors deem unreliable in this setting, but by the tactile scratching sensation of the needle touching the stone and by fluoroscopic observation of the stone moving when contacted.

Because no contrast study confirms entry into the collecting system, the team inferred correct guidewire placement indirectly from the wire’s coiling pattern. Two patterns were identified as almost confirming placement within the pelvicalyceal system: a ‘Ureteric line’ (U) pattern and an ‘Upper pole-pelvic’ (UP) pattern. If the guidewire could not be negotiated past the calculus, a small volume of normal saline was injected through the cannula to create space between the stone and the calyceal mucosa before re-negotiation. Fluoroscopy in different planes was used to check for erratic guidewire patterns suggesting a position outside the collecting system, and ultrasound was kept on standby as a backup check.

Patient selection was deliberately strict, and this is central to interpreting the findings. Inclusion required stone morphology that clearly depicted the pelvicalyceal pattern, such as partial or total staghorn stones; solitary or multiple calyceal stones located within one centimetre of the calyceal tip; pelvic stones accompanied by calyceal stones; and absence of gross hydronephrosis. Calyceal stones needed to exceed one centimetre to ensure adequate fluoroscopic visibility and a palpable scratch feel. Exclusions covered pelviureteric junction stones with gross hydronephrosis, absence of a calyceal stone, calyceal stones more than one centimetre from the calyceal tip, anterior calyceal stones, residual stones after prior surgery, and small stones lacking visibility or tactile feedback. The authors acknowledge that both the one-centimetre stone size and the one-centimetre distance thresholds were set arbitrarily.

All operations were performed prone under general anaesthesia by a surgeon with more than twenty years of experience and more than 10,000 PCNL procedures. For the first twenty-four cases, a retrograde ureteral catheter was inserted as a safety measure in case stone-guided puncture failed; as experience grew, this step was omitted and reserved only for failed punctures. Tract dilatation proceeded to 18 to 24 French depending on stone burden, with an 18 French sheath and mini-nephroscope for stones of two to three centimetres and larger sheaths for bigger stones. Stones were fragmented with a holmium laser or pneumatic lithoclast, and all patients received a double-J stent and a nephrostomy drain. Dilatation was deliberately limited to the distal stone margin, a wilful underdilatation meant to guard against misplaced tract extension.

The outcomes were favourable across the recorded variables. Mean operative duration was 54.45 plus or minus 8.46 minutes, measured from first puncture to wound closure. The surgeon rated intraoperative visualisation of the collecting system and stone as excellent in 54 of 56 rated cases, 96.4 percent, and moderate in the remaining two. The postoperative haemoglobin drop averaged 0.9 plus or minus 0.7 grams per decilitre and the creatinine change averaged 0.3 plus or minus 0.7 milligrams per decilitre, neither statistically significant, with p values of 0.32 and 0.442 respectively. Stone-free status, defined as no residual fragments of four millimetres or larger on a non-contrast CT scan 24 hours after surgery, was achieved in 53 cases, or 94.6 percent, while three cases, 5.4 percent, had residual stones.

Complications were rare and mild. Two of 56 cases, 3.6 percent, experienced complications, all classified as Clavien-Dindo grade I, the mildest category. The authors note this aligns with a large collaborative review in which 88 percent of PCNL cases had Clavien grades of zero or I. Guidewire patterns were the U pattern in 38 cases, 67.9 percent, and the UP pattern in 18 cases, 32.1 percent. Notably, when the punctured stone sat in an upper or mid calyx, the U pattern appeared in 15 of 16 cases, and for upper calyceal stones it appeared in all four. Stone-guided puncture succeeded in every case, and the team did not need retrograde contrast or ultrasound to confirm guidewire position in any doubtful scenario.

Context from prior research underscores why the result is notable but also why caution persists. In a randomised trial cited by the authors, blind fluoroscopy-only puncture achieved calyceal entry in only 50 percent of cases with a stone removal rate of 62 percent, alongside 12 percent inadvertent direct pelvic punctures, and its authors concluded the blind technique alone was not sufficiently reliable. The only directly pertinent prior study, by Ayokapan and colleagues, compared direct-guided puncture without contrast to standard PCNL and found comparable outcomes with reduced operative time. The authors also point out that omitting retrograde catheterisation can reduce radiation exposure, urinary tract trauma, operative and anaesthesia times, and costs, though they caution this justification collapses when puncture safety is in doubt, since a stone-guided puncture without contrast or ultrasound does not display the collecting system anatomy and carries theoretical risks of infundibular or organ injury.

The study’s limitations are substantial and the authors state them plainly. As a retrospective cohort, it is vulnerable to selection bias, its small sample constrains statistical power and generalisability, and every procedure was performed by one highly experienced surgeon, so the results cannot be assumed to transfer to less experienced operators. Parameters such as puncture time, first-pass success rate, and number of punctures were not recorded, and published first-pass success rates elsewhere range from 58 to 100 percent. The guidewire coiling pattern, while consistent, does not guarantee entry into the collecting system even with multiplanar fluoroscopy. The authors call for prospective randomised trials in carefully selected cohorts to validate the technique, and conclude that sg-PCNL is a safe and effective alternative to conventional methods, in terms of operative duration, visualisation quality, and safety, only within this select group of patients and only in experienced hands.

Subject of Research: Stone-guided puncture for percutaneous nephrolithotomy without contrast pyelography or ultrasound guidance

Article Title: Feasibility and safety of stone-guided puncture in percutaneous nephrolithotomy in a select group of patients

Article References: Chakraborty, J. N., Sharma, D., & Adhikari, H. (2026). Feasibility and safety of stone-guided puncture in percutaneous nephrolithotomy in a select group of patients. African Journal of Urology, 32(1), Article 61. https://doi.org/10.1186/s12301-026-00609-y

Image Credits: AI Generated

DOI: 10.1186/s12301-026-00609-y

Keywords: percutaneous nephrolithotomy, kidney stones, stone-guided puncture, fluoroscopy, urology, stone-free rate, retrospective cohort study, Clavien-Dindo complications, guidewire pattern, calyceal puncture, surgical technique, patient selection