Spatial arrangement and syntopy of the kidney
The kidneys are located in the retroperitoneal space, with their upper poles displaced medially and posteriorly relative to the lower ones. The renal pelvis (pelvis renalis) anatomically faces anteriorly and medially. Because the upper segments often lie above the level of the 11th–12th ribs, access to them may require passing the needle through the intercostal space.
When planning a puncture, it is necessary to consider the mutual arrangement of adjacent structures. An erroneous trajectory risks damaging the pleura, diaphragm, liver, spleen, or colon. Atypical bowel anatomy, such as a high and posterior position of the splenic flexure (common in obese women), dictates the mandatory use of ultrasound guidance before the intervention. With an intercostal approach, one must remember the intercostal artery. To avoid hitting it, the puncture is recommended to be performed through the posterior half of the intercostal space, avoiding a cranial (upward) direction of the needle.
Architectonics of the pelvicalyceal system
Normally, an adult has 8 to 9 renal calyces. The polar calyces are usually fused together, making them larger and technically more convenient for instrument introduction.
The optimal choice for a basic puncture is the posterior calyx. It is located closer to the patient's skin and forms an almost straight trajectory to the neighboring anterior calyces and renal pelvis, which significantly simplifies intrarenal navigation. Using an anterior calyx as the entry port makes navigation extremely difficult.
If the ultimate goal of the intervention is the ureteropelvic junction or the ureter itself, surgeons prefer an upper-pole or interpolar approach. Puncturing the lower pole for manipulations on the ureter is impractical due to the unfavorable angle.
Vascular anatomy and rules for safe access
The main renal artery branches into a massive anterior and a thinner posterior branch. Inside the organ, they divide into segmental and lobar branches, and then transition into arcuate arteries (arteriae arcuatae), which arch around the necks of the calyces peripherally.
The main safety principle in nephrostomy is to puncture strictly into the center of the calyx. Attempting a puncture through the neck (infundibulum) or directly into the renal pelvis risks rupturing the main arteries.
The instrument must pass through Brödel's line (Brödel line), an avascular zone at the boundary of the blood supply from the anterior and posterior branches. Special attention should be paid to the posterior branch of the renal artery: this is the only large vessel running behind the collecting system. When the patient is in the prone position, this artery is extremely vulnerable if the puncture site is chosen too medially.
Structural anomalies and basic instruments
The classic picture involves a single renal artery and a single vein. However, up to 25% of patients have accessory arteries, and 3–17% have venous anomalies. These developmental variants do not change the basic rules for choosing the puncture site, but they explain why rare hemorrhagic complications occur even with flawless technique.
Primary access to the collecting system is achieved using needles. Specialists typically choose one of two options: a micro-puncture system with an ultra-fine 21-G needle or a standard single-component set including an 18-G needle and a 4-F introducer.
Briefly: answers to topical questions
What structures form the intercostal neurovascular bundle, which is vulnerable during access to the upper pole of the kidney?
The intercostal neurovascular bundle vulnerable during access to the upper pole of the kidney includes the vein, artery, and nerve. They are located in the costal groove from top to bottom in the following order:
- Intercostal vein (v. intercostalis) — occupies the highest position.
- Intercostal artery (a. intercostalis) — runs along the lower margin of the rib and is vulnerable during puncture if the needle is directed cranially.
- Intercostal nerve (n. intercostalis) — occupies the lowest position.
What types of contrast media are used for antegrade pyelography after renal pelvis puncture?
Contrast medium and gas for double-contrast visualization are used for antegrade pyelography and visualization of the pelvicalyceal system.
- Radiopaque agent / contrast medium — injected into the pelvicalyceal system during antegrade pyelography to visualize it.
- Gas (air or CO2) — used in double-contrast pyelography. The gas is injected slowly, in a volume of no more than 20 ml, under constant fluoroscopic control; it rises to the non-gravity-dependent parts, i.e., the posterior calyces.
"Posterior is straight, anterior is curved." In percutaneous access from the back, puncturing the posterior calyx provides a straight path to the renal pelvis, whereas an anterior approach requires complex and traumatic instrument bends.
Class and exam questions
Why is it necessary to puncture precisely into the center of the renal calyx during percutaneous access?
Large arcuate arteries run along the periphery of the calyx in the area of its neck. Puncturing off-center drastically increases the risk of their rupture and massive bleeding.
Through which calyx is it best to gain access to the ureter?
Access via the upper-pole or interpolar calyx is optimal. The lower pole creates too sharp an angle for the successful passage of instruments into the ureter.
What is the danger of the intercostal approach to the upper pole of the kidney?
Intercostal puncture carries the risk of damaging the pleura as well as the intercostal artery, which runs along the lower margin of the rib. To protect the artery, the needle should not be directed cranially.
What is Brödel's line and why is it needed?
This is a relatively avascular plane in the renal parenchyma located between the supply zones of the anterior and posterior arterial branches. Passing the instrument through this line minimizes blood loss.
What else to study on this topic
- Percutaneous nephrolithotomy (PCNL)
- Antegrade ureteral stents: placement and monitoring
- Balloon dilation of ureteral strictures
- Management of urinary leaks and urinary fistulas
- Suprapubic catheterization and management of non-deflating balloons
- Ablation of renal cysts and lymphoceles
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