Question

Suppose a calculus (stone) is blocking a major calyx, what effect might this have on capsular hydrostatic pressure (CIIP) and thus on net filtration pressure (NFP)?

Answer 1

The renal calyces are the chambers in the kidney that urine travels through. The apex of the renal pyramids is surrounded by smaller calyces. Urine generated in the kidney travels into the minor calyx through a renal papilla at the apex; two or three minor calyces merge to form a major calyx, through which urine passes before continuing via the renal pelvis into the ureter.

Complete answer:
When a stone or calculus blocks a large calyx, the capsular hydrostatic pressure rises, resulting in a decrease in net filtration pressure. $C1IP$ increases as a result of the stone's resistance. Because the net transit of filtrate is reduced due to the blockage, net filtration pressure drops across the glomerulus.
Kidney stones, also known as nephrolithiasis, are hard masses formed by crystals that separate from urine in the urinary tract. Urine normally contains chemicals that prevent or hinder the formation of crystals. These inhibitors do not appear to work for everyone, and stone formation can occur.

Note:
The hydrostatic force exerted on the plasma filtrate by the elastic recoil of the glomerular capsule, which tends to push water and dissolved solutes from the plasma filtrate back into the capillaries of the glomerulus, is known as capsular hydrostatic pressure (CHP). The total pressure that facilitates filtration is known as NET FILTRATION PRESSURE (NFP). We eliminate the forces that oppose filtering from the GBHP to get NFP. $NFP = 55 - \left( {15 + 30} \right) = 55 - 45 = 10mm{\text{ }}Hg$ is a typical NFP (using the figures above).