Indian Journal of Urology
: 2012  |  Volume : 28  |  Issue : 4  |  Page : 473--474

Staghorn morphometry for percutaneous nephrolithotomy

Sagorika Paul 

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Paul S. Staghorn morphometry for percutaneous nephrolithotomy.Indian J Urol 2012;28:473-474

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Paul S. Staghorn morphometry for percutaneous nephrolithotomy. Indian J Urol [serial online] 2012 [cited 2023 Feb 5 ];28:473-474
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Percutaneous nephrolithotomy (PCNL) is the standard treatment for staghorn calculus. Unfortunately there is no consensus on the precise definition of staghorn calculus. [1] The term "staghorn" is often used to define any branched stone occupying more than one portion of the collecting system. Classification of "partial" or "complete" staghorn calculus also does not imply any specific criteria of volume. [1] Using CT Urography (CTU),the authors developed staghorn morphometry-based prediction algorithm to predict tract(s) and stage(s) for PCNL and classify staghorn calculus accordingly.

This was a retrograde study, including a total of 170 renal units in 163 patients who underwent treatment for staghorn calculi. This study was from September 2009 to December 2010. Patients with renal insufficiency (n = 38) and nonfunctioning renal units (n = 18) were excluded. All underwent 16 slice CTU before surgical treatment. All attempts were made to completely clear the stones using bare minimum tracts possible with judicious use of rigid and flexible nephroscopes / ureteroscopes in the prone and Valdivia position. Stone-free status (SFRs) was assessed after the completion of surgery and subsequent follow-up after 3 months. CTU depicting the staghorn morphometry and pelvicaliceal anatomy was analyzed using CT scan volumetric assessment software (3D-DOCTOR-TM). CT software calculated the total stone volume (TSV) with absolute volume and percentile volume in the pelvis, entry calyx (EC), favorable calyx (FC) and unfavorable calyx (UC).

TSV was defined as the stone volume calculated by reconstructing the entire stone image on the software and pelvic stone volume (PSV) as volume calculated by reconstructing the component of the stone present in pelvis. EC was the optimum calyx selected in relation to ribs, adjacent viscera and the ability to retrieve maximum stone burden. The percentage volume of the stone in the EC was defined as entry calyx stone percentile volume. A FC was the calyx containing stone that was obtuse to the EC and infundibulum width >8 mm. On the contrary, an UC was acute to EC with infundibulum width <8 mm. The percent of the stone in these calices to the TSV was similarly defined as FC and UC stone percentile volume, respectively.

The inference obtained by CTU analysis was retrospectively applied to clinical per operative data to identify correlation between the staghorn morphometry and tract(s) and stage(s) needed. There was no significant difference in TSV when single or two tracts were compared but there was significant increase for more tracts. Pelvic, FC, pelvic and EC stone percentile volume were significantly lower in the multiple tract group. UC stone and UC stone percentile volume were significantly less in single and two tract(s) than with multiple tract groups.

The staghorn morphometry was also correlated with stages of PCNL. Increasing stone volume resulted in increasing stages. The single stage procedure had significantly lesser TSV and PSV. UC stone volume and percentile stone volume was more in multiple stage procedures.

A model based on TSV and UC stone percentile volume was determined [Table 1].{Table 1}

Based on predicted model for achieving clearance by PCNL, type 1 staghorn would necessitate single tract and stage; type 2, single tract-single/multiple stages or multiple tract-single stage; and type 3, multiple tracts and stages.


The concept of tract and stage is clinically important for planning PCNL monotherapy for staghorn calculus. For staghorn calculus, single tract does not render optimum clearance from all caliceal extensions. [2] Single tract access is indicated for small burden staghorn stones. [3] Although the stone clearance rate is superior with multiple tract access but it is associated with more hemorrhagic complications. [4] The other advantage of staging is to increase the SFRs under the same hospital stay by doing relook nephroscopy. The disadvantages of multiple staged PCNL monotherapy includes increased hospital stay, patient costs, and decreased hospital turnover. Therefore, it is preferable to reduce tract and stage whenever feasible, while maintaining highest level of stone clearance.

The major determinant for tract and stage is staghorn morphometry. A collecting system with favorable anatomy, allows single tract easy nephroscopy into each calyx due to wide infundibulum and spacious collecting system. A compact collecting system with narrow infundibulum may not permit easy nephroscopy through a single tract. A friendly collecting system with a large TSV and a corresponding large stone volume in an UC still requires a separate tract for clearing the unfavorable caliceal stone. Thus, CTU-based staghorn morphometry could offer an accurate morphometric data required for PCNL planning for staghorn calculus. However, such classifications have a drawback of being cumbersome and turn out to be useful in research setting only. [5]


1Preminger GM, Assimos DG, Lingeman JE, Nakada SY, Pearle MS, Wolf JS Jr; AUA Nephrolithiasis Guideline Panel). Chapter 1: AUA guideline on management of staghorn calculi: Diagnosis and treatment recommendations. J Urol 2005;173:1991-2000.
2Soucy F, Ko R, Duvdevani M, Nott L, Denstedt JD, Razvi H. Percutaneous nephrolithotomy for staghorn calculi: A single center's experience over 15 years. J Endourol 2009;23:1669-673.
3Akman T, Sari E, Binbay M, Yuruk E, Tepeler A, Kaba M, et al. Comparison of outcomes after percutaneous nephrolithotomy of staghorn calculi in those with single and multiple accesses. J Endourol 2010;24:955-60.
4Hegarty NJ, Desai MM. Percutaneous nephrolithotomy requiring multiple tracts: Comparison of morbidity with single-tract procedures. J Endourol 2006;20:753-60.
5Mandal S, Goel A, Goyal NK. Re: Staghorn Morphometry: A New Tool for Clinical Classification and Prediction Model for Percutaneous Nephrolithotomy Monotherapy. J Endourol 2012;26:)6-14. J Endourology. article in press