October 2026 English edition · Evidence reviewed through October 3, 2026 · David Shusterman, MD

Appendix C: The Glossary of Urological Anatomy

To take ownership of your stone risk, you need a working vocabulary of the urinary tract. Medical terminology should clarify the system, not distance you from it. This glossary translates the principal structures and procedures used throughout the book into practical language.

The Filtration Plant

Nephron. The microscopic functional unit of the kidney. Each nephron filters blood, reabsorbs needed water and solutes, and helps create urine. Nephron number varies among individuals and generally declines with aging and kidney injury.

Glomerulus. A capillary filtration unit at the beginning of the nephron. It allows water and small dissolved substances to enter the tubular system while normally retaining blood cells and most large proteins.

Renal cortex and medulla. The cortex is the outer kidney tissue containing glomeruli and portions of the tubules. The medulla is the deeper tissue organized into pyramids that concentrate urine and deliver it toward the collecting system.

Loop of Henle. A U-shaped segment of the nephron that helps establish the concentration gradient needed to conserve water. Concentrated urine can raise supersaturation when mineral loads are high or fluid intake is inadequate.

Renal papilla. The tip of a medullary pyramid where urine drains into a minor calyx. Many calcium stones begin near papillary surfaces.

Randall’s plaque. Calcium-phosphate deposits beneath the papillary lining that may serve as attachment sites for some calcium oxalate stones. Not every stone arises from a visible plaque.

Calyx and calyces. Cup-shaped collecting spaces receiving urine from the renal papillae. Minor calyces join into major calyces and then into the renal pelvis.

Renal pelvis. The central funnel that gathers urine before it enters the ureter.

Hydronephrosis. Dilation of the kidney’s collecting system. It can occur when urine drainage is obstructed, but the degree of dilation does not by itself establish the cause, severity, or duration of obstruction.

Staghorn calculus. A branching stone occupying a substantial portion of the renal pelvis and calyces. Some are infection-related, but composition must be established rather than assumed.

The Transport System

Ureter. The muscular tube carrying urine from the kidney to the bladder through coordinated contractions called peristalsis.

Ureteropelvic junction (UPJ). The transition between the renal pelvis and upper ureter. It is one potential site of narrowing or stone impaction.

Ureterovesical junction (UVJ). The point where the ureter traverses the bladder wall. Distal ureteral stones commonly lodge near this segment.

Hydroureter. Dilation of the ureter, usually above a point of impaired drainage.

Urothelium. The specialized lining of the renal pelvis, ureters, bladder, and proximal urethra. Persistent or unexplained hematuria may require evaluation of this lining according to the patient’s risk profile.

Bladder. A muscular storage organ that receives urine from both ureters and empties through the urethra.

Urethra. The final channel through which urine exits the body.

Devices and Procedures

Ureteral stent. A temporary internal tube extending from kidney to bladder to maintain drainage. Stents can be lifesaving in infected obstruction and useful after selected procedures, but they may cause urgency, frequency, hematuria, flank discomfort, or pelvic pressure.

Nephrostomy tube. A drainage catheter placed through the back directly into the kidney. It may be used for urgent decompression or as part of a percutaneous procedure.

Ureteroscopy. Endoscopic passage of a small scope through the urethra and bladder into the ureter or kidney. Stones may be dusted with laser energy, fragmented, or removed with baskets.

Shock-wave lithotripsy (SWL/URS). External acoustic pulses focused on a stone to fragment it. Effectiveness depends on stone size, location, density, body habitus, anatomy, and the ability of fragments to clear.

Percutaneous nephrolithotomy (PCNL). Removal of kidney stones through a tract created from the skin into the collecting system. It is commonly favored for large or complex renal stone burdens.

Ureteral stricture. Scar-related narrowing of the ureter. It may result from prior inflammation, impacted stones, surgery, radiation, or other causes.

Adjacent Anatomy and Mimics

The prostate surrounds the upper male urethra and can contribute to retention, frequency, urgency, or incomplete emptying. In women, ovarian, uterine, gastrointestinal, and musculoskeletal disorders can mimic stone symptoms. A uterine fibroid is a benign smooth-muscle tumor arising from the uterine wall; depending on its size and position, it may compress adjacent structures, including a ureter.

The point of this vocabulary is not self-diagnosis. It is informed participation. When you understand where a stone is located, whether drainage is impaired, and what a proposed device or procedure actually does, shared decision-making becomes more precise.