|Year : 2015 | Volume
| Issue : 2 | Page : 131-136
Microscopic hematuria in athletes: A review of the literature
Hamdan H Alhazmi
Department of Surgery, King Saud University, Riyadh, Saudi Arabia
|Date of Web Publication||6-May-2015|
Hamdan H Alhazmi
Department of Surgery, Division of Urology, King Saudi University, Riyad
Source of Support: None, Conflict of Interest: None
Microscopic hematuria in athletes is a frequent laboratory sign result from vigorous exercise after a period of rest, either in individual sports as running and swimming or in clash sports such as boxing and football. This could be due to renal trauma and/or bladder injury or vasoconstriction of the splanchnic and renal vessels also due to constriction of the efferent glomerular arteriole lead to release of red blood corpuscles and plasma proteins in urine. Such hematuria is a benign self-limited condition 48-72 h. However, other urinary tract problems should be excluded. It is estimated that microscopic hematuria was 18% in athletes immediately after and 3 days post race. This article presents an overview of the current knowledge of microscopic hematuria in athletes focusing on etiology, pathophysiology, diagnosis and treatment. This information should assist healthcare practitioners who treat patients with this disorder.
تعد البيلة الدموية المجهرية من أكثر المؤشرات المخبرية شيوعا بين الرياضيين الناتجة عن ممارسة الرياضات الحيوية بعد فترة من الخمول الجسدي. وذلك إما في الرياضات الفردية كالجري والسباحة أو رياضات الاشتباك كالمصارعة وكرة القدم ويرجع سبب هذا إلى حدوث رضوض بالكلى أو المثانة أو انقباضات بالأوعية الدموية الحشوية والكلوية. أيضا نتيجة لانقباض الشريان الكبيبي الصادر والذي يؤدي إلى الهيموجلوبينية والمايوجلوبينية وعلى الرغم من كونها حالة عرضية مؤقتة تتراوح مدتها بين 48-72 ساعة إلا أنه لابد من استبعاد أى اضطرابات أخرى بالجهاز البولي هذا. وقد تم رصد النسبة المؤية لحدوث مثل هذه التغيرات بعد الممارسة الرياضية بمدة لا تزيد عن ثلاثة أيام وكانت النتيجة 18% من الحالات تم تشخيصها على أنها بيلة دموية مجهرية. هذا المقال يلقي الضوء على المسببات، والفيزيولوجيا المرضية والتشخيص والعلاج مما قد يساعد الطاقم الطبي في معالجة مثل هذه الحالات
Keywords: Athletes, hematuria, microscopic
|How to cite this article:|
Alhazmi HH. Microscopic hematuria in athletes: A review of the literature. Saudi J Sports Med 2015;15:131-6
| Introduction|| |
Microscopic hematuria in athletes is appearance of occult blood in urine of athlete after vigorous exercise  by a period not more than 3 days.  If dipstick test is positive for blood, the amount is determined by microscopic examination and result is confirmed if three or more red blood corpuscles are seen per high power field microscope on two of three specimens.  It is often detected accidentally, or it will remain undetected  usually this's come after a period of rest and lasts for 48-72 h as it is self-limited.  Otherwise, urinary tract disease should be excluded.  Type of exercise has the effect on the amount of blood, but it should be strenuous.  Microscopic hematuria is either traumatic or nontraumatic. Vasoconstriction of the splanchnic and renal vessels during exercise leads to redistribution of blood to skeletal muscles, which cause hypoxic damage to nephron and increase in glomerular permeability with increase in excretion of red blood cells (RBCs) and protein into urine, constriction of efferent glomerular arteriole increase filtration pressure and thus more release of RBCs depending on rapacity of exercise.  Asymptomatic exercise hematuria has no specific treatment.  In general, exercise hematuria is preventable, and sports men should be aware of it to avoid development of anemia if blood loss repeated,  however, periods of prolonged rest should be avoided. 
| Biomechanics|| |
Main function of the kidney is purification and filtration of blood from impurities through renal circulation. Renal blood flow is the volume of blood delivered to the kidneys per unit time; blood reaches the kidney through aorta, renal arteries, segmental and lobar as well as lobular arteries till end at the afferent arterioles which are minute arterial vessels entering the nephron in bowman's capsule.  Nephron is the functional unit of the kidney formed of tubular structures; Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting duct. Furthermore formed of vascular structures entangling with the tubules: Afferent arterioles, glomerular arterioles in the glomerulus, efferent arterioles and vasa recta.  The process of filtration depending on the flow of blood in the glomerular capillaries depending on the hydrostatic pressure gradient between afferent and efferent arteriole, which determine the glomerular filtration rate 60 mm Hg (hydrostatic pressure of blood) − (32 mm Hg osmotic pressure + 18 mm Hg capsular hydrostatic pressure) = 10 mm Hg outward.  Glomerular filtrate normally does not contain cells because they are too large to be filtered in the pores, thus; urine normally does not contain neither cells (RBCs, white blood cells, platelets) nor plasma proteins.  The afferent arteriole has a wider diameter than the efferent arteriole. This causes some additional pressure. The afferent arteriole is a larger arteriole than usually supplies capillaries and hence it has a higher pressure. 
| Etiology and pathogenesis|| |
Traumatic causes of microscopic hematuria have been described after a variety of forms of exercise contact sports such as football, boxing, and noncontact sports like long-distance running, rowing, spinning and swimming.  Direct blow to the kidney or bladder may cause hematuria, however; bladder injury may occur with running, cycling and horse riding due to the up and down movement. Striking manner of strenuous sports can lead to repeated impact of the bladder wall against the base.  Empty bladder make surfaces of the bladder opposed, which increase the possibility of trauma, also repeated collisions of perineum with saddle of bike or horse is a cause. 
Nontraumatic causes are the main bulk of the issue because during strenuous high intensity exercise whether it is contact or noncontact there are some changes occur in the bio physiology of the body specially in nontrained bodies because they couldn't in short time compensate, accommodate and adapt to changes of sprint strenuous exercises.  During exercise sympathetic nervous system takes the upper hand fight, flight and fright also sympathomimetic fast acting and slow acting hormones released like renin, angiotensin, aldosterone, antidiuretic hormone, cortisol, epinephrine and growth hormone which increase specially - the later-in running, all of this neuro-hormonal response to exercise lead to raised heart rate, blood pressure, and renal blood pressure. Vasoconstriction of renal artery to redistribute the circulation to skeletal contracting muscles, which cause renal ischemic damage at the level of the nephron leading to widening of the pores of glomerular capillaries and increased permeability to the extent that RBCs can be filtered and appear in urine.  In addition, vasoconstriction of efferent arteriole increases the glomerular capillary hydrostatic filtering pressure that promotes the release of RBCs in urine.  Another cause is the accumulation of lactic acidosis after anaerobic metabolism result from vigorous exercise increases glomerular permeability, lead to the passage of erythrocytes into the urine.
Nutcracker syndrome is a compression of left renal vein between the aorta and superior mesenteric artery that may cause congestion and kidney becomes studded with blood favoring bloody urine. It causes microscopic and gross hematuria associated with left flank pain, not only in Asian children, but also in adults. 
All that should be separated from two causes of hematuria postexercise called brown urine of athletes (sports hematuria), which are myoglobinuria due to rhabdomyolysis; and hemoglobinuria caused by RBCs trauma. In blood vessels of the feet specially in running athletes with abnormalities in proteins of membranes of RBCs; however all types of exercise induced hematuria are similar in being self-limited unless there are underlying renal or general cause of hematuria.  In addition, exercise induced hematuria exacerbated in patients with glomerular diseases like immunoglobulin A (IgA) nephropathy. 
| Risk factors|| |
Being an athlete is a risk factor for microscopic hematuria especially if you remain a period far from stadium and this point criticized by many researches before for example urine samples from 50 athletic runners before and after, on 3 successive days after a long race. They found that all urine samples were negative for blood before race. About 18% of the samples showed microscopic and macroscopic hematuria after the race.  After four sets of 30 min running 70% of runners, showed proteinuria and no microscopic hematuria noticed because of the height and high altitude where the marathon held.  Some studies found that young age athletes in high risk of hematuria when compared to their older compatriots.  Positive family history of hematuria may have a role as a risk factor. Also medications like aspirin and penicillin may increase the possibility of bleeding.  Some studies stated that just stress and vigorous exercise is a risk factor for hematuria called jogger syndrome.  Age and sex are not determinants unless there are underlying causes like enlarged prostate in old males, recurrent urinary tract infection in females, and on contrary, Alport syndrome and hereditary nephritis in males, patients with smoking history, more exposure to benzene, dyes, underlying urinary tract diseases and irradiation.  Furthermore, some sports either contact or noncontact are of higher risks than other sports as running, horse riding, mountain biking, cycling, rowing, swimming, and spinning, also boxing and football all are risky sports. 
| Signs and symptoms|| |
Athletic exercise induced microscopic hematuria is usually a trivial condition which almost passed unnoticed, so it is asymptomatic, and only discovered accidentally on routine investigations by urine dipstick and urine analysis. However in some studies, they stated that about 7.2% of athletes suffer from Microscopic hematuria had mild to moderate flank colicky pain which relieved soon by analgesics, but this pain may come as a result of trauma which is one of the causes of hematuria.  Many papers assume that frequent repeated undetected and untreated microscopic exercise hematuria happened to an athlete may lead to the appearance of chronic blood loss symptoms like, fatigue, weakness, palpitation, dizziness and tinnitus.  In general, hematuria may associated with other symptoms related to the underlying cause, but it is quite far from exercise hematuria as it has no symptoms like; abdominal pain, back pain, painful micturition, urgency, frequency, fullness, headache, fever, chills, and anuria.  However, it is worthy to be mentioned; that it was estimated that hematuria occurs in 2.5-21% of the whole population without symptoms and without underlying the cause. In six populations, different researches revealed high prevalence of asymptomatic idiopathic microscopic hematuria in 16-21% of them. ,
Sign of traumatic microscopic exercise induced hematuria can be addressed in signs of trauma to loin region, which are redness, hotness, swelling, bruises, laceration, peeling or bleeding. 
| Investigations|| |
Microscopic hematuria detected by urine dipstick limited specificity, if it is positive for blood so microscopic hematuria confirmed by appearance of three or more red blood corpuscles per high power field microscope on two of three specimens to be appropriately evaluated. Many organizations recommend no screening for asymptomatic microscopic hematuria, so investigations will be done if we intentionally are searching for exercise microscopic hematuria. Therefore, the initial step should be microscopic examination of the urine precipitate from freshly deflated, midstream urine sample. , Quantitatively, we can count the number of RBCs/ml urine or examination of the centrifuged urinary residue. However, high risk patients with >3 RBCs/HPF should be subjected to full urological evaluation, and almost a primary cause will be revealed as discovered in research population where 32-100% of them have underlying cause behind hematuria.  Furthermore, presence of red cell casts, proteins, dysmorphic red cells or any pathognomonic finding pointing to renal parenchymal disease, glomerular disease, lower urinary tract problem which may require further interventional investigation as inverted phase contrast microscopy, however all these new lab findings may even refer to underlying systemic diseases like endocarditis, hepatitis, infections, malignancy, vasculitis and lupus erythematosus. Glomerular diseases like crescent glomerulonephritis, IgA nephropathy, membrano-proliferative glomerulonephritis. Renal parenchymal disease like analgesic nephropathy all of which renal biopsy should be done, if negative so isolated hematuria may be considered and follow-up of these patients may show hypertension or renal failure 1 day.  Patients with persistent hematuria should undergo upper urinary tract imaging and cystoscopy of the urinary bladder and cytological evaluation of exfoliated cells in the urine sample. Patient should perform repeated urinalysis 2 days after activity if the cause behind hematuria is reasonable and physiological like in menstruation, sex, strenuous exercise, and trauma. Obviously, clean catch urine should be obtained or otherwise we should use catheter if it is hard to be obtained as in obesity and vaginal contamination.  Intravenous urography, computed tomography and ultrasonography might be valuable in cases with persistent hematuria.
| Differential diagnosis|| |
Microscopic hematuria is the symptom of differential diagnosis that can be easily misinterpreted; the following differential diagnosis can be suggested like; systemic diseases or source outside genitourinary system like; endocarditis, systemic lupus erythematosus, vasculitis, coagulation deficits, hypertension, neoplasms, thrombocytopenic pupura, tuberculosis, rectal or gynecological source may cause hematuria. 
Any problems which might affect the genitourinary system; renal vascular system, kidney, renal pelvis, ureters, urinary bladder, urethra, prostate, testis, genital duct system and genital covering skin might cause hematuria as:
Atrophic kidney, polycystic kidney, Alport's hereditary nephritis, pelvic kidney, duplicate collecting system, scarred kidney, calyceal diverticulum, bladder diverticulum.
Urethral disruption (seen in pubic fracture), bladder injury (seen in pelvic fracture), renal laceration or rupture, renal contusion or trauma.
Acute poststreptococcal glomerulonephritis, hemorrhagic cystitis, infection anywhere in genitourinary system, pyelonephritis, mycobacterial cystitis, radiation cystitis, interstitial cystitis, eosinophilic cystitis, inflammation of the urethral trigon.
Benign prostatic hyperplasia, malignant tumor anywhere in genitourinary system or metastatic tumor anywhere, bladder papilloma, urethral polyp or bladder neck polyp.
Renal vein thrombosis, renal artery occlusion, abdominal aortic aneurysm renal artery stenosis, renal arteriovenous fistula, bladder varices, papillary necrosis.
Nephrolithiasis, bladder stones or calculus anywhere in genitourinary system.
Henoch-Schonlein purpura, IgA nephropathy, thin glomerular basement membrane disease.
Cyclophosphamide, gold, penicillamine, nsaids, warfarin.
Urethral stricture or meatal stenosis, ureteropelvic junction obstruction, hydronephrosis, bladder neck contracture.
Benign essential hematuria, renal cyst, renal parenchymal disease, vesicoureteral reflux, cystocele, phimosis, ureterocele, trabeculae bladder, isolated hematuria, brown urine of athlete. 
| Management|| |
Prevention of exercise induced hematuria can occur by multiple means as modification of strenuous vigorous exercise program of long duration to be a less stressful, light and efficient program. Avoidance of dropout and discontinuity of training for a long time, avoid risky sports as mentioned and if it has to be, so, safety precautions has to be followed according to type of sport; for example: For contact sports like football, rugby, American football, basketball, fight sports, baseball, softball, ice hockey, field hockey, lacrosse, martial arts, paintball or other contact sports. Athletic cup innovative protective cup supports, provides comfort and protection of perineum and testis. Another way is to hire certified athletic trainees with experience in medicine and precautions as well as sports not just a personal athletic. 
For noncontact sports generally we should follow some measures like wear a protective gear, give yourself plenty of time to warm up and cool down. Do not involve in a game unless you know everything about it; rules, risks, precautions and measures, watch out others and communicate with team members so as not to hurt anybody unintentionally and finally don't play when you feel tired or injured. 
Some sports have specific precautions like horse riding, the cycling pad and cycling should protect the body, whose weight exerts vertical pressure on the saddle, at the level of perineum and testis. The rider can then focus on his pedal instead of shocking with discomfort and pain that result from striking of perineum and testis against horse back or bike seat, it also help avoidance of perennial shafting, make the athlete count 100 pedal strokes/minute. ,
Biking should be launched under strict safety precautions like seat adjustments, bike seat should be installed according to gender. Seats are designed to distribute weight across differently shaped perinea, to avoid chafing. Wider bike seat will be more suitable for athletes whose pelvic bones wider than their seats, or try cushy seat to be more comfortable and distribute pressure properly when you sink in it. To avoid chafing you should decrease pelvic rotation by lowering the seat if it is too high, or tilt it to a horizontal position if it is angled too high. Stand up on the pedals every 10 min during ride to relieve pressure or when you ride over rugged terrain. 
In swimming, you should make short fast kicks instead of slow extended kicks. Keep your hips centered and body balanced by pointing your toes to extend flippers, so your hips will float to the top of the water's surface, and hence, shaking movement of hip region will be diminished and possibility of traumatic hematuria diminished too. 
Some researches stated that to run correctly, which would reduce tiring, injury and make running enjoyable. Head kept straight. Avoid hunching shoulders to allow more oxygen to reach muscles. Hands kept relaxed. Arms kept at 90°. Lean forward during running. Avoid bending forward and backward at the level of the waist as it will load pressure on hips and it will cause up and down striking movement leading to repeated impact of the bladder wall against the base. So running in an upright position reduces heel strike and helps landing on middle of foot keeping hips stable and forward facing. Avoid sticking bottom out or move hips side to side. To absorb impact of running on hard surfaces we should land with slight bending of knees and lifting those forwards without elevating them too high and we should also avoid bouncing up and down. Avoid striking the ground heavily with the heel or on the forefoot first and land below the hips. Run lightly and quietly and not hit or slap the ground heavily whatever your weight. Empty bladder make surfaces of the bladder opposed which increase the possibility of trauma, also repeated collisions of perineum with saddle of bike or horse is a cause. ,,
Treatment of such hematuria is not a serious issue unless there was underlying cause. Then the concentration will be shifted toward treatment of the cause and sequential complications. Otherwise in asymptomatic microscopic exercise induced hematuria nothing to be done except reassurance and prevention of recurrence and persistence by safety measures following, supplementation of iron to avoid chronic blood loss problems like anemia and supplementation of drugs that strengthen capillary walls, RBCs membranes and efficacy of platelets and coagulation system. 
| Conclusion|| |
Safety measures and precautions that mentioned before play an important role in avoidance of traumatic causes of microscopic exercise induced hematuria in athletes. In spite of being trivial self-limited frequent symptom, healthcare staff should not underestimate the condition without investigation. Because another underlying cause may be found accidentally underneath, moreover, early screening and protection of high-risk trainees and high risk sports for such type of microscopic exercise induced hematuria, and proper treatment and supplementation protect the player from unpleasant squeal of this condition.
| Recommendations|| |
- Make sports medicine a separate branch of medicine in healthcare that will enable injuries to be identified early and speed up recovery
- Precautions mentioned should be taken in consideration while training to avoid traumatic causes of hematuria
- Avoid being too long time away and far from training
- Consider the possibility of presence of underlying cause of hematuria
- Early screening of high risk trainees and sports, and proper treatment and supplementation protect the player from unpleasant squeal
- This review opens an access for further research especially in effect of safety measures and management implementation on the incidence and prevalence of such type of hematuria and control of its complications.
| Acknowledgment|| |
Special thanks and gratitude to Dr. Ahmed Elmalky, M.Sc., who provide his help in review process.
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