You’re carefully emptying Mr. Henderson’s urinary drainage bag at the end of your shift, noting the amount and color on his intake and output (I&O) sheet. While you’re measuring that fluid, you’re witnessing the final result of millions of tiny workers inside his kidneys called nephrons doing their job.
What is a Nephron?
The nephron (NEF-ron) is the microscopic functional unit of the kidney. You can think of it as a tiny filtering factory found inside each kidney. Healthy kidneys contain about one million of these per kidney! Their main job is to filter waste products, excess water, and impurities from the blood. These waste materials are then turned into urine, which flows to the bladder, while the cleaned blood returns to circulation.
Why Nephron Matters in Your Daily Care
Even though you can’t see them with your eyes, the health of your residents’ nephrons dictates almost everything you do regarding fluid balance and elimination. When nephrons are damaged by chronic conditions like diabetes or high blood pressure, the body loses its ability to clean the blood and regulate fluid. This is why strict Intake and Output (I&O) monitoring is vital. You are essentially tracking whether these microscopic filters are keeping up with the body’s needs or failing.
What You’ll See During Your Shift
You won’t see a nephron directly, but you will see the evidence of their work—or their decline. You will encounter residents with Chronic Kidney Disease (CKD) or those on dialysis, which means their nephrons have stopped working. You might measure urine that is bloody, dark, very concentrated, or extremely scant. You will also manage strict fluid restrictions for residents whose nephrons can no longer process excess water.
“Nurse, I emptied Mr. Henderson’s foley and he only had 150cc of output for the whole shift. His urine is also very dark amber. His feet look pretty swollen today, too. I’m worried his kidneys aren’t filtering.”
Common Pitfall & Pro Tip
⚠️ Pitfall: Treating Intake and Output (I&O) recording as just “busy work” or guessing the amounts. Inaccurate I&O gives the medical team a false picture of how well the nephrons are functioning.
Pro Tip: Be precise. If a resident spills water or vomits, estimate it and document it. Remember that every drop counts—accurate urine output is often the first red flag that nephrons are struggling.
Memory Aid for Nephron
Think “N” for Nephron, “N” for Nature’s Strainer”.
Just like a strainer keeps pasta and lets water through, the nephron keeps blood cells and lets waste/water through (as urine). If the strainer gets clogged or broken (disease), the water doesn’t drain properly.
State Test Connection
This term appears on CNA exams under Anatomy and Physiology or Basic Nursing Skills. You may be asked, “What is the functional unit of the kidney?” The answer is always the nephron.
Related Care Concepts
Understanding the nephron connects directly to your role in monitoring Intake and Output (I&O), recognizing signs of dehydration (when the body tries to conserve fluid), and observing edema (swelling from fluid retention when filters fail). It is also the basis for understanding dialysis treatments and why residents with kidney issues have specific dietary restrictions on potassium or protein.
Quick Reference
✓ Key function: Filters blood to create urine and regulate fluid balance ✓ When to report: Decreased urine output (oliguria), sudden swelling (edema), or changes in urine color ✓ Care reminders: • Be exact when measuring I&O • Report urine that is bloody, cloudy, or has a strong odor immediately • Encourage fluids if not restricted to help kidneys flush waste • Note skin changes—itching can occur when nephrons aren’t filtering toxins well
Bottom line: While you can’t see them, protecting your residents’ kidney health starts with your accurate observations at the bedside.