Excretory Products and their Elimination

The loop of Henle, together with the vasa recta, sets up the counter-current mechanism that builds an increasing osmotic gradient in the medullary interstitium (from about 300 mOsm/L in the cortex to about 1200 mOsm/L in the inner medulla).
This gradient allows water to be reabsorbed from the collecting duct, which produces a concentrated (hypertonic) urine. Mammals can thus conserve water.
Without the loop of Henle, no medullary gradient would form. Water could not be withdrawn from the collecting duct, so a large volume of dilute urine would be formed. Filtration would still occur, so urine would still be produced.
So if Henle's loop were absent, the urine would be more dilute.