Glycosuria Renal

 

A)Points on renal glycosuria in pregancy : Normally in nonpregnant  state 1300 ml is the renal blood flow per minute & 180  Liter is the GFR  (glomreural   filtration load)  per 24 hours of which 178.5 liter is reabsorbed in 24 hrs  by loop of Henle(both ascending  loop & descending  loop )  by countercurrent mechanism  and only 1.5 lit of total 180 Lit Glomerular  fluid  is excreted in urine. In pregancy total urine volume will increase due to more renal plasma flowà More GFR.

B)   As there is accelerated  blood flow in kidneys’ in preg so total Glom filtrate comes to about 182-185 Liter  due to hyper dynamic circulatory state  .This causes increased Glom filtrate load  including much glucose which many kidneys can’t handle at Loop level  .

C)  As because   tubules are not empowered  for reabsorption of  excess glucose load present in tubular fluid , therefore some glucose remains unabsorbed  which come out of the in urine.  Normally 100% glucose is reabsorbed and 98% Albumin (69000 mol weight) is reabsorbed so we see urine albumin report as “TRACE” .

D)                   Hb mol is 68000 and can free pass  through  Glo capillaries (if haemolysis) and are not reabsorbed in tubules.   As such faced  with more than excess glucose content in Henle loop  Tubules can’t reabsorb entire glucose  .As such some amount of glucose is passed in urine not due to primary renal defect but as an effect of hyper dynamic state of circulatory system Albumin molecules slightly larger in volume in comparison to Haemoglobin molecule usually unable to pass the glom capillaries unless endotheliosis occurs . So albumin can only pass the glomeruleral filtrate if there is some damage in glomerural   capillaries (endothelial dysfunction) but Hb molecule can easily pass. That implies haemoglobinuria can occur without renal Glo capillary damage but for albuminuria to occur there should some degree of damage (endotheliosis/ or auto immune damage SLE ) to Glo capillaries be it of any etiology.

E) In pregancy what happens the total 24 glomerular excretion load exceed about 20% due to maternal changes .As such loop of Henle are unable to reabs the total glucose excreted by glomeruli àleading to glycosuria.