7.9 Kidneys & GU Tract - Prevent Dialysis 1

Physician's Notebooks 7  - http://physicians notebook.blogspot.com

Genito-Urinary Tract - Update 24 Aug. 2021. (The chapters 7.9 to 7.14 recently got a major update after several years with the assistance of James Stim, my son, a nephrologist.  So these chapters represent the latest on renal dialysis to the end of 2021)

9.

 Introduction

The kidneys act like filters of the blood and make the fluid that becomes urine. Blood from descending aorta goes to each kidney via left and right renal artery; in the kidneys the blood plasma is passed through millions of micro-filtering units (glomerulus; plural "glomeruli"), which allow water and small molecules like glucose to pass easily but block larger molecules, and then the filtered fluid flows down the tubule that drains each glomerulus. In the tubule, nutrients like glucose and important mineral ions like Na⁺, K^+, Cl^-  and ions like bicarbonate HCO3-(minus 1 charge) get absorbed into the blood or secreted into the tubular fluid and similarly with the water molecule (H₂O) which gets reabsorbed or excreted under the influence of the anti-diuretic hormone (ADH) to keep the water and electrolytes balanced. The fluid that becomes urine results from the filtration and from tubular re-absorption and secretion, and this pre-urine flows down millions of tubules atop each kidney into a larger collecting tube, the ureter, on each side and both ureters empty into the urinary bladder and the urine exits from bladder through the urethra. In men it passes the prostate-narrowing posterior (or upper) urethra tube to be urinated out from the penis and, in women, urinated out of urethral opening in the cleft in upper slit of vulva just below the clitoris.

   On a usual diet with free fluid intake, the 2 kidneys can pass 2 liters or more urine per 24 hours; their capacity to excrete water is huge (e.g., with normal kidneys we can drink many liters water a day and it will be urinated out over the next hours). If forced to go without water longer than 24 hours, the urine output will drop to less than 300 ml (0.3 L) per 24 hours, and the person will experience much thirst, and if it continues, his body dehydrates and he dies.

   Arterial Blood Pressure (BP) change - low or high - may be an important sign of kidney disease. Certain kidney diseases with damage to the renal tubules reduce the kidneys' ability to reabsorb water and the result is too much loss of salt and water in urine and the BP drops too low unless one constantly drinks water. It is seen in badly infected kidneys and with poisoning. But more often, kidney failure results in clog of the kidneys' filtering capacity and overloads the system with water, leading to high blood pressure, heart failure and stroke from brain hemorrhage. An increase in body water from kidney failure gives over-hydration and shows edema swelling of feet, hands and face.

   The kidneys' filtering prevents protein loss. Early, important sign of failing kidney is the micro appearance of protein in urine. Gradually this increases to a point of protein deficiency seen in blood test of total protein level and another cause of body swelling edema, starting in the feet.

   Failing kidneys will signal need for dialysis by the rising nitrogen products – the blood urea nitrogen (BUN) and the creatinine (Cr). Monitoring the blood Cr is an important part of a healthy longevity program because rising Cr is the best blood test measure of failing kidneys.

   A finer and more accessible screening test is using urine test strips to monitor for protein in urine; done by urinating onto the Dipstick strip and reading color change. Repeated test finding of as low as 30 mg/100 ml protein (trace albumin, or microproteinuria on Dipstick) may predict early chronic kidney disease that years later could lead to dialysis.
   END OF CHAPTER.  To read next now, click 7.10 Kidney Failure/Dialysis Prevention 2