Haematuria (blood in urine) is a common reason for “Red Urine” in patients with Kidney and Urinary tract diseases.
If you consult your doctor for reddish discoloration of your urine, your doctor will first:
Based on the clinical examination, you will be advised necessary laboratory-based tests to confirm the presence of blood in your urine.
These tests would also allow your doctor to get an approximate idea of where the blood could have been coming from, into your urine.
LABORATORY TESTS
1. URINALYSIS
A Routine Urinalysis (URE) usually serves as the pivot for confirming the presence of red blood cells in urine. It involves the following components:
Physical Analysis
A urine sample that appears Reddish to cola coloured as opposed to the standard normal urine colour (Pale/straw yellow to dark yellow) may indicate the presence of blood in urine. This is the commonest cause of Red Urine in members with Kidney or urinary tract disease and warrants further confirmation.
Chemical Analysis
The Chemical Dip strip test is one of the most sensitive tests available for detecting blood in urine.
Method:
The dip-strip meant for detecting blood in urine is dipped in the urine sample briefly, removed and assessed for the respective colour change after 1 minute. The intensity of colour change serves as a reference against the quantity of blood present in the sample. This reference range varies between different “Dip-strip” kits, and a reference colour chart is provided by the dip-strip manufacturing company.
NOTE:
These chemical dip-strips chiefly detect the quantity of the red pigment in blood — “Haemoglobin” – in the sample instead of RBCs themselves. For Haematuria, the urine sample must have whole red blood cells and not just the red pigment of blood. This requires confirmation under a Microscope.
Microscopic Analysis
Analyzing the urine sample under a microscope is the most direct & reliable method to confirm the presence of Red Blood Cells (RBCs) in Urine.
The presence of blood in urine is always abnormal.
But did you know? When found in a urine sample, the shape and size of RBCs in urine is a fairly reliable way to guess where the blood may be coming from.
In fact, your pathologist’s observation here is essential for your doctor at the clinic to decide on your further course of laboratory tests & treatment.
Read on, to understand how this works.
First things first, what do your RBCs normally look like in a normal “blood” sample?
Red blood cells (RBCs) are disc-like in shape with “pinched in”centers from either side. Each RBC spans 7 – 8 micrometers in diameter and 2 – 2.5 micrometers in thickness.
The image below shows numerous RBCs (pink circular structures) in a normal “blood” sample as seen under a microscope.
Please note:
1 micrometer (µm) is a thousand times smaller than 1 millimeter (mm) and a thousand times larger than 1 nanometer (nm)
It is important that you remember the size of an RBC and the relative measures above, to understand why & how the shape of RBCs helps to approximately determine the site of bleeding into the urine.
A urine sample with Haematuria, could either have:
- Fresh, RBCs with normal shape & size (Iso-morphic RBCs) OR
- Distorted, shrunken RBCs with blebs (Dys-morphic RBCs)
Urine samples positive for Red Blood Cells (RBCs) as observed under a Phase-contrast microscope (CC 4.0); A – Urine sample containing RBCs of normal shape and size (Iso-morphic RBCs); B – Urine sample containing distorted RBCs showing irregular borders & blebs (Dys-morphic RBCs)
SO HOW DOES A URINE TEST HELP YOUR DOCTOR DIAGNOSE THE POSSIBLE SITE OF BLEEDING?
Red blood cells act somewhat like modelling-clay when they pass into our urine. Looking at its shape and size, a pathologist (Lab doctor who checks your urine) can comment on where those RBCs might be coming from.
ISO-MORPHIC RED BLOOD CELLS IN URINE
If RBCs get to pass through a path that’s “wide enough” to accommodate their entire span of 7-8 micrometres (µm) comfortably, they appear in urine still retaining their normal shape and size. The Urine outflow pipe (Ureter) – one originating from each kidney, down to our bladder and outside (urethra) is more than at least 3 millimeters (mm) wide from the inside, all throughout. This is over 300 times the span of a single RBC.
Hence, conditions that arise along these parts namely the Renal pelvis, Ureters, Urinary bladder, prostate (in males) or the Urethra, that cause bleeding into urine show RBCs of normal shape & size in Urine.
To read the list of such causes please refer to the “Table enlisting conditions associated with Haematuria.”
DYSMORPHIC RED BLOOD CELLS IN URINE
Conversely, if RBCs need to force through tiny pores not meant for them to normally use in good health or “push & shove” through their channel of passage or are forced to stack-up against each other, they face a lot of mechanical “trauma”. Ultimately, such RBCs lose their beautiful, smooth borders and become shrunken, full of blebs and sometimes spiny in appearance.
This can happen if RBCs end up force-squeezing themselves through tiny pores in our delicate filtration zones in our kidneys (glomerulus) that separate blood from wastes. These various pores range from 0.025 to 0.15 micrometres (µm) which is about 280 times smaller than 1 RBC. Further, RBCs would need to make their way through tiny tubes in our nephrons where they can stack-up against each other before being “force-washed” into the urine. All these squeezing forces end up badly distorting RBCs that ultimately appear in the urine as Dys-morphic RBCs.
All conditions that damage the kidney filtration zones and bleed through the glomerulus (Glomerular Haematuria) would show up Dysmorphic RBCs in Urine in course of the respective disease.
FURTHER TESTING TO CONFIRM THE ROOT CAUSE
Once Haematuria is confirmed, you may need further clinical consultations, so your doctor can take a detailed case history. To pinpoint why you have blood in your urine, you will be advised about further tests.
These will include:
Your blood-work
Imaging scans like an Ultrasound scan (USG), CT-scan and/or an MRI scan
In some cases, a Biopsy may be necessary. Here, a tiny section of living tissue from within your body is removed with a syringe & studied under a microscope to look for specific characteristics of a suspected disease state.
After diagnosis of the root cause of Haematuria, your doctor will initiate a suitable cause-specific treatment plan for patients.
Click here to read about the general principles of this topic.
REFERENCES
- Medscape ( https://emedicine.medscape.com/article/981898-workup )
- NIDDK (https://www.niddk.nih.gov/health-information/urologic-diseases/hematuria-blood-urine)
