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[Medscape]: 引起尿液变色的12种原因
2017年12月03日 临床话题, 基本知识 暂无评论

12 Causes of Discolored Urine

Christopher S Atalla, DO; Josh Palka, DO | November 15, 2017

Adapted images courtesy of Regensburger M, Huttner HB, Doerfler A, Schwab S, Staykov D. Springerplus. 2014;3:551. [Open access.] PMID: 25332856, PMCID: PMC4192142.

Normal urine coloration ranges from clear to yellow. However, a multitude of pathologies and agents can change the color and/or clarity of urine. This slideshow discusses several potential causes of abnormal urine color.

The neurologic imaging studies and urine samples were obtained in an elderly woman who underwent mild hypothermia therapy for an atypical intracerebral hemorrhage. The dark green urine on the center left occurred 48 hours following propofol administration. Reversal of the urine color to normal yellow ( center right) occurred a few hours after cessation of the propofol infusion.

Image courtesy of Josh Palka, DO.


The urine bag shows gross hematuria in an elderly male with a malpositioned Foley catheter. The catheter balloon was found in the prostatic urethra.

Hematuria, defined as the presence of red blood cells (RBCs) in the urine, [1] is one of the most common urologic problems that clinicians encounter. It may present microscopically (>3 RBCs per high-powered field [HPF]) or be grossly visible to the naked eye, with the potential source of the RBCs ranging from the renal glomerulus to the urethral meatus. [1]

A myriad of genitourinary pathologies can cause hematuria—ranging from benign conditions such as urinary tract infections or vigorous exercise to much more concerning etiologies such as bladder or kidney cancer. Once benign conditions have been ruled out, further evaluation is required. [1]

Work-up of hematuria per American Urology Association guidelines includes imaging of the upper urinary tracts. This is done via computed tomography urography (CTU) (gold standard) or noncontrast renal CT scanning, non-contrasted magnetic resonance imaging, or ultrasonography with retrograde pyelography. [1] These imaging modalities are used to evaluate for renal carcinoma or upper tract urothelial carcinoma. Evaluation of the bladder with CT or ultrasound is not sensitive or specific enough to evaluate for carcinoma in-situ and therefore, is performed by direct visualization via cystoscopy. Urinary cytology may be useful as an adjunct to help rule out malignant changes within the urinary tract after an initially negative evaluation or in patients with risk factors for carcinoma in-situ (smoking) and irritative voiding symptoms. [1]

Image courtesy of Josh Palka, DO.

Iatrogenic urinary tract trauma

The image depicts a Foley catheter malpositioned within the prostatic urethra in the same patient discussed in the previous slide. Severe gross hematuria resulted from this placement.

Proper insertion of urinary catheters can be challenging in male patients with significantly enlarged prostates. Thus, it is essential to know how to safely insert the catheter into the bladder such that the balloon does not expand within the prostate.

When using a Foley catheter, it is important that (1) insertion is to the hub to ensure the balloon is past the prostate and (2) urine return is seen to further ensure the balloon will not be within the urethra when it is inflated.

If resistance is met during the insertion of a Foley catheter in a male patient, use of a coude catheter may be attempted as it has a stiffer, angled tip, which allows the catheter to navigate past the enlarged prostate.

Scanning electron microscopic image of E coli courtesy of the Centers for Disease Control and Prevention/Janice Haney Carr.

Urinary tract infections

Urinary tract infections (UTIs) may also lead to hematuria, [1] with Escherichia coli one of the most common causative organisms. [2]In one population study comprising 3108 women with acute cystitis, E coli was isolated in approximately 78.6% of the urine cultures obtained. [3]

Treatment for acute uncomplicated cystitis consists of antibiotic therapy, commonly with trimethoprim-sulfamethoxazole, nitrofurantoin, or fosfomycin. [2]

Ciprofloxacin is no longer recommended for uncomplicated UTIs. A May 2016 US Food and Administration (FDA) safety communication warned of potential disabling side effects associated with the use of fluoroquinolones for these and other uncomplicated conditions. [4]

Image courtesy of Josh Palka, DO.


Another cause of gross hematuria is trauma. Shown is a 67-year-old male who presented to the ER as a pedestrian versus automobile accident. An abdominal and pelvic CT with IV contrast was obtained (after previous images were obtained with contrast) and revealed a right Grade IV renal laceration with laceration through the collecting system and active extravasation from posterior of the right kidney in addition to other polytrauma.

The kidney is the genitourinary organ most commonly injured in trauma. Trauma to the kidneys can be managed conservatively and, if needed, angioembolization of the kidney can be performed. Surprisingly, the degree of hematuria does not correlate well with the degree of the trauma. Renal lacerations are graded from one to five, one being the least severe and five being the most severe. Details are listed on the American Association for the Surgery of Trauma website.

The patient shown developed a delayed bleed and underwent angiography with selective embolization.

Image courtesy of Chris Atalla, DO.

"Purple urine bag syndrome" (PUBS) is a rare phenomenon caused when UTIs with bacterial strains that produce indoxyl phosphatase (eg, Providencia stuartii, P rettgeri, Klebsiella pneumoniae) react with the synthetic materials of urinary catheters/bags.[5]

When PUBS occurs, it is typically found in elderly patients with constipation and long-term indwelling urinary catheters in association with colonization with the above bacteria as well as with E coli, Morganella morganii, Pseudomonas aeruginosa, andProteus and Enterococcus species. [5]

Clinicians should keep in mind that PUBS is not entirely a benign condition, because it points to underlying recurrent UTIs and, potentially, the improper care of urinary catheters and/or improper hygiene. [5,6]

Image courtesy of Josh Palka, DO.


The image reveals bladder cancer found in an elderly former smoker who presented with a four-month history of painless gross hematuria.

A major concern for patients with gross hematuria is the possibility of urothelial cancer in the bladder. Globally, urothelial bladder cancer is the 7th most common cancer in men and the 17th most common neoplasm in women. [7] Smoking or a previous history of smoking is the most common risk factor for this disease. [7] Commonly, patients present with complaints of irritative voiding symptoms that may mimic urinary tract infections (e.g., dysuria, hematuria, and urinary frequency) with no growth found on urine cultures. It is imperative that patients be further evaluated with cystoscopy to ensure no underlying malignancy, carcinoma in-situ is commonly missed.

Additionally, patients on anticoagulation therapy should be evaluated in similar fashion as those not on anticoagulation therapy as spontaneous hematuria from blood thinners alone should not occur.

Image courtesy of Josh Palka, DO.

Delayed CT urogram images were obtained in a middle-aged male with a two-month history of painless gross hematuria. CT scanning revealed a large filling defect in the bladder consistent with a bladder tumor. Cystoscopy demonstrated a large tumor. The patient underwent transurethral resection of the bladder tumor and was found to have stage pT1 disease (invasion into the lamina propria).

Image courtesy of Josh Palka, DO.

Another potential cause of hematuria is renal cell carcinoma (RCC), which accounts for 2%-3% of all cancers in the United States and about 85% of malignant kidney tumors. [8] RCC is also the sixth and eighth most common cancer in US men and women, respectively. [8]

Of note, obesity is a risk factor for, and has a linear relationship with, RCC, especially in women. Additionally, individuals with von Hippel-Lindau syndrome are at higher risk for RCC: Up to 30% develop this malignancy, with nearly 70% of affected patients having RCC by age 60 years; RCC is also a major cause of death in these patients. [9]

Nephron-sparing surgery has become the treatment of choice for smaller RCC tumors, with one case series showing no local recurrence. [10] However, this type of procedure is more technically difficult to perform and requires the proper selection of patients.[11]

The image shows RCC in a young adult female following robot-assisted laparoscopic partial nephrectomy. The mass was found on incidental CT scanning for a possible kidney stone.

Image courtesy of Josh Palka, DO.

Benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is another common cause of gross hematuria, occurring due to the vascularity of the primary gland itself or as a result of vascular prostatic regrowth after transurethral resection of the prostate (TURP). [12] An indication for TURP is gross hematuria that is not amenable to medical therapy with 5-alpha-reductase inhibitors such as finasteride. [12] This procedure may be especially helpful in men with larger prostates (>30-40 g). [13]

The image shows a TURP operation in progress utilizing a bi-polar loop to remove prostate tissue to open the urethral channel and cauterize any bleeding vessels identified.

Image courtesy of Josh Palka, DO.


Kidney stones are one of the most common pathologies that may cause gross or microscopic hematuria. An estimated 1 in 11 people in the United States are affected (8.8% prevalence), up from 1 in 20 people in 2004, with men more likely to develop nephrolithiasis than women (10.6% vs 7.1%, respectively). [14]

Multiple risk factors for the formation of kidney stones exist, with many metabolic and/or dietary in nature. Obesity is a known risk factor: As the incidence of obesity rises, so too does that of kidney stone disease. [14] Between 1971 and 2006, the incidence of obesity more than doubled (14.6% to 34.1%) in the United States. [15] Overall US obesity rates slightly increased between 2007 and 2014 (34.7% to 36.4%) [16]; currently, more than one third of US adults (36.5%) are obese. [17]

One frequent dietary cause of nephrolithiasis is diminished or lack of proper fluid intake. [18,19] Another dietary etiology is increased intake of oxalate from foods such as black tea, dark chocolate, rhubarb, spinach, and certain types of nuts. [20] Patients with recurrent kidney stone formation should undergo a metabolic evaluation and 24 hour urine study to elucidate any potential reversible causes of their kidney stones.

The image shows ureteral stones that were removed with laser lithotripsy from a patient who presented with left flank pain and painless hematuria in the emergency department.

Image courtesy of Nunn R, Chang N, Milner SM, Price LA. Eplasty. 2013;13:ic16. [Open access.] PMID: 23409207, PMCID: PMC3558850.


Myoglobinuria is usually the result of rhabdomyolysis, typically caused by trauma or alcohol/drug abuse. [21] The tea-colored urine that develops is commonly confused with gross hematuria, as both may not only look similar to the untrained eye but also cause positive findings on a urinalysis dipstick. These two conditions can be differentiated by centrifuging the urine. If the urine has a clear center, the cause of the discoloration is myoglobinuria, whereas if there is a reddish sediment, the etiology is likely to be hemoglobinuria. [21] Creatinine kinase levels will also be elevated in myoglobinuria.

Rhabdomyolysis presents with nonspecific findings, of which the three hallmarks are muscle weakness, myalgia, and dark urine. [21]Therefore, clinical suspicion is paramount to avoid potentially life-threatening complications such as acute kidney injury and disseminated intravascular coagulation. [21,22]

The work-up of myoglobinuria includes obtaining levels of creatinine kinase and electrolytes, as well as assessment of renal function with measurements of blood urea nitrogen (BUN) and creatinine. The main goal of therapy in patients with rhabdomyolysis is hydration for prevention of acute kidney injury with preservation of kidney function. [21,22]

The image depicts myoglobinuria found in a young adult male following a high-voltage electrical injury that resulted in rhabdomyolysis.

Image courtesy of Josh Palka, DO.


Any patient with a chronic indwelling urinary catheter will have a 100% rate of bacteriuria, [23] which may develop into pyuria, wherein white blood cells (or pus) are present in the urine.

To minimize the risk of infections, urinary catheters and suprapubic catheters should be changed every 3-4 weeks. [24] When possible, bladder emptying should be managed with clean intermittent catheterization to reduce the risk of bacteriuria and infection.[23]

The pyuria shown occurred in a T5 paraplegic man with suprapubic tube in place.

Image courtesy of Josh Palka, DO.


Bilirubinuria may be a sign of increased bilirubin in the blood stream and an indication of hepatocellular or cholestatic disease (eg, hepatitis, cirrhosis, choledocholithiasis). [25,26] Only the conjugated form of bilirubin is found in the urine, as unconjugated bilirubin is typically bound to albumin and not normally filtered by the kidneys. [25]

As is the case with myoglobinuria, patients with bilirubinuria have a brownish discoloration to their urine [26] that may be confused for gross hematuria.

The bilirubinuria seen in the urine samples were collected from an elderly jaundiced male with autoimmune hepatitis.

Image courtesy of Wikimedia Commons/ James Heilman, MD.



Phenazopyridine is available as a prescription and over-the-counter medication for the relief of urinary discomfort, burning, and pain—symptoms commonly caused by UTIs. [27] Because this agent is an azo dye, it can cause an orange discoloration of the urine.

Phenazopyridine has no antibacterial component and, as such, should be used only as adjunct to antibiotics. Caution should be taken prescribing this medication to patients with renal or liver disease. [27,28]

Image of green urine discoloration due to propofol infusion courtesy of Shioya N, Ishibe Y, Shibata S, et al. Case Rep Emerg Med. 2011;2011:242514. [Open access.] PMID: 23326690, PMCID: PMC3542914.


Green urine is a highly uncommon and unusual finding, generally associated with recent surgery requiring high doses of propofol infusion. [29] The discoloration may result from quinol derivatives following glucuroconjugation and excretion of the parent drug.

Green urine may also occur with the use of a prescription medication (Uribel) that is similar to phenazopyridine for the relief of urinary discomfort. [30] This medication contains methylene blue and, when mixed with urine, tends to discolor urine green.

Adapted image courtesy of Viswanathan S. ISRN Nephrol. 2013;2013:215690. [Open access.] PMID: 24959539, PMCID: PMC4045424.

Paraphenylenediamine Dye Toxicity

Paraphenylenediamine is a highly toxic ingredient of hair dye formulations that can cause acute kidney injury and result in black urine. [31] The renal damage is likely multifactorial—including direct toxic effects on renal tubular cells, hypovolemia, hemolysis, and rhabdomyolysis—and may require dialysis.


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