Question

. Mr. Smith, who has alcoholic cirrhosis (liver disease), has noticed significant swelling (edema) to his lower extremities that he no longer can put on his shoes. a. What do you think is the cause of his edema? Explain your answer. b. If his NFP at the arteriole side of the capillary bed is +10 mm Hg, what would you expect it to be at the venule end, positive or negative? Explain while discussing hydrostatic and osmotic pressures in the capillaries and interstitial fluid and define NFP. State the equation for calculating NFP.

Answer 1

a) Cirrhosis slows the normal flow of blood through the liver , thus increasing pressure in the vein that brings blood to the liver from the intestines and spleen.

The increased pressure in the portal vein can cause fluid to accumulate in the legs (edema)​​​​​​ and in the abdomen (ascites).

b)Net filtration rate :

The net filtration rate represents the interaction of the hydrostatic and osmotic pressure , driving fluid out of the cappillary.

It is equal to the difference between the CHP (capillary hydrostatic pressure) and BCOP (Blood colloid osmotic pressure).

Since filtration is , by definition the movement of fluid out of the capillary , when reabsorption is occuring , the NFP is a negative number.

NFP changes at different points in a capillary bed .

If NFP at arteriole side of the capillary bed is +10mm Hg , thus drives a net movement of fluid out of the capillary at the arterial end.

At the middle the net movement is zero.

At the venous end of the capillary , there is an NFP of -7 mmHg.

Thus at the venule end the NFP is negative .

The equation for calculating NFP is :

NFP = Glomerular blood hydrostatic pressure (GBHP) - Colloid hydrostatic pressure (CHP) + Blood colloid osmotic pressure (BCOP ).