Corpus: Renal pelvis

The renal pelvis is the collecting space of the kidneys for the urine dripping from the papillary ducts (renal papillae, papillary ducts). In its course, the renal pelvis tapers into the ureter, the connection between the kidney and the urinary bladder.

In clinical anatomy, the term "renal pelvis" is usually used to refer only to the wide main space of the renal pelvis, while the renal calices are considered separately. Both components are then summarised as the renal pelvic calyx system (NBKS).

The renal pelvis is made up of a system of renal calices (Calix renalis):

Calices renales minores[Bearbeiten]

The calices renales minores, or "small renal calices", each enclose one to three renal papillae, like an egg cup encloses an egg. There are about 10 small renal calices on one kidney.

Calices renales majores[Bearbeiten]

The small renal calices unite to form 2 large renal calices (calices renales majores), which in turn unite to form a common space. This pelvic space eventually tapers into the ureter.

The calyx system can have two forms

• Ampullary type: The renal calices are short and open directly into a common space without first forming the calices renalis majores.
• Dendritic type: The renal calices are long and appear tree-like due to their branching.

The renal pelvis is located in the renal sinus at the level of the 1st-2nd lumbar vertebrae, about 3-6 cm from the lateral edge of the vertebral bodies. Like the kidney, the renal pelvis is therefore also located in the retroperitoneum. Surgical access is usually via the patient's back.

• Tunica mucosa: It consists of transitional epithelium and lines the inside of the renal pelvis.
• Tela submucosa: A thin layer between the mucosa and the muscularis.
• Tunica muscularis: A well-developed muscle layer consisting of bundles of smooth muscle cells. It ensures the further transport of urine with peristaltic waves.
• Tunica adventitia: This layer of connective tissue connects the renal pelvis with the surrounding tissue of the retroperitoneal space.

The calyx system and the renal pelvis are already part of the urinary tract, as the urine is only collected and passed on in them. The pacemaker cells for the peristalsis of the ureters are also located here.

The renal pelvis can be affected by the following diseases, among others:

• Pyelonephritis: inflammation of the renal pelvis
• Urolithiasis: renal pelvis stones

• Image source podcast: © David Becker / Unsplash