Doorway information about patient
The patient is a 20-year-old man who comes to the clinic due to dark urine for 5 days.
Vital signs
Temperature: 36.7 C (98 F)
Blood pressure: 122/80 mm Hg
Pulse: 74/min
Respirations: 14/min

Question

Quizplus · Accepted Answer

The Answer is Approach to the patient
Patients may report unusual or undifferentiated symptoms that could be due to disease in multiple systems. In some cases, this may represent a cardinal manifestation of an uncommon condition (eg, the "target shaped" rash of Lyme disease). Alternately, unusual symptoms may be an atypical manifestation of a common disorder (eg, systemic lupus erythematosus presenting as migratory mononeuropathy).
When evaluating a patient with nonspecific symptoms, review the medical history, risk factors, and medications to identify what disorders and complications are most likely. Identify the system involved, and consider what disorders are most likely to affect that system in the patient.
Dark urine can represent either an unusually concentrated urine, hematuria, or an abnormal pigment in the urine. Abnormal urine color is usually due to disorders of the renourinary tract, hepatobiliary system, blood/hematologic system, or musculoskeletal system. If the patient otherwise feels well, abnormal urine color is usually benign.
Differential diagnosis
The color of the urine can guide the differential diagnosis:
Red: Blood, food pigments (eg, beets, rhubarb), medications (eg, phenazopyridine, rifampin), porphyrins
Blue/green: Food dyes, medications (eg, indomethacin, amitriptyline), Pseudomonas urinary tract infection
Brown: Medications (eg, metronidazole, senna), liver/kidney disease, myoglobin/rhabdomyolysis
Orange: Hepatobiliary disease, dehydration
Hematuria can be categorized by the pattern through urination. Blood at the start of voiding that clears is usually from a urethral source. Blood at the end of voiding suggests a bladder or prostate source. Visible blood throughout voiding may represent an upper tract (kidney and collecting system) source.
Biliary obstruction may cause dark-yellow/orange urine with jaundice, pale stools, and right upper quandrant pain. Hematuria in a patient with a history of heavy smoking is a common presentation of bladder cancer. Dark urine following a crush injury or extreme physical exertion suggests rhabdomyolysis. In addition, hemolysis may cause dark urine with fatigue, jaundice, and back or abdominal pain.
History and physical examination
In addition to the standard general medical history and physical examination, the following sections include the most common items that should be included in the evaluation of a patient with dark urine.

<strong>Approach to the patient</strong> Patients may report unusual or undifferentiated symptoms that could be due to disease in multiple systems. In some cases, this may represent a <strong>cardinal manifestation</strong> of an uncommon condition (eg, the target shaped rash of Lyme disease). Alternately, unusual symptoms may be an <strong>atypical manifestation</strong> of a common disorder (eg, systemic lupus erythematosus presenting as migratory mononeuropathy). When evaluating a patient with nonspecific symptoms, review the medical history, risk factors, and medications to identify what disorders and complications are most likely. Identify the system involved, and consider what disorders are most likely to affect that system in the patient. Dark urine can represent either an unusually concentrated urine, hematuria, or an <strong>abnormal pigment</strong> in the urine. Abnormal urine color is usually due to disorders of the renourinary tract, hepatobiliary system, blood/hematologic system, or musculoskeletal system. If the patient otherwise feels well, abnormal urine color is usually benign. <strong>Differential diagnosis</strong> The color of the urine can guide the differential diagnosis: <strong>Red</strong>: Blood, food pigments (eg, beets, rhubarb), medications (eg, phenazopyridine, rifampin), porphyrins <strong>Blue/green</strong>: Food dyes, medications (eg, indomethacin, amitriptyline), Pseudomonas urinary tract infection <strong>Brown</strong>: Medications (eg, metronidazole, senna), liver/kidney disease, myoglobin/rhabdomyolysis <strong>Orange</strong>: Hepatobiliary disease, dehydration <strong>Hematuria</strong> can be categorized by the pattern through urination. Blood at the start of voiding that clears is usually from a urethral source. Blood at the end of voiding suggests a bladder or prostate source. Visible blood throughout voiding may represent an upper tract (kidney and collecting system) source. <strong>Biliary obstruction</strong> may cause dark-yellow/orange urine with jaundice, pale stools, and right upper quandrant pain. Hematuria in a patient with a history of heavy smoking is a common presentation of <strong>bladder cancer</strong>. Dark urine following a crush injury or extreme physical exertion suggests <strong>rhabdomyolysis</strong>. In addition,<strong> hemolysis</strong> may cause dark urine with fatigue, jaundice, and back or abdominal pain. <strong>History and physical examination</strong> In addition to the standard general medical history and physical examination, the following sections include the most common items that should be included in the evaluation of a patient with dark urine. <strong>Closing the encounter</strong> In the wrap-up discussion, the first step is to discuss the likely diagnosis along with an assessment of the diagnostic uncertainty. If a patient has pathognomonic findings for a particular disease, you should explain the significance of them. If you are uncertain about the diagnosis, say so clearly, but reassure the patient that you will work with them to identify the cause. Regarding diagnostic tests, if invasive studies are necessary (eg, cystoscopy in an elderly smoker with hematuria), explain the rationale for the tests. Allow time for questions, and assess the patient's readiness to undergo the studies you recommend. <strong>Diagnostic studies</strong> Patients with an abnormal urine color should have a urinalysis with microscopic analysis of urinary sediment (ie, for casts, crystals, etc.). Note that patients with myoglobinuria may have a positive test for hemoglobin on chemical ( dip stick ) urinalysis without red blood cells on microscopic analysis. Other studies may include: Electrolytes, blood urea nitrogen, creatinine Liver function tests (eg, direct and indirect bilirubin) Urine culture Complete blood count (and peripheral smear, reticulocyte count) Muscle enzymes (eg, creatinine kinase, aspartate aminotransferase [AST]) CT urogram (for identifying kidney stones) Liver/biliary CT scan, ultrasound Cystoscopy Patients with hematuria should have evaluation of both the upper and lower urinary tract. Typical studies include CT urogram and cystoscopy, but the specific evaluation may be individualized. If hemolytic anemia is suspected, start with a complete blood count, reticulocyte count, and peripheral smear. Supportive findings include elevated lactate dehydrogenase, low haptoglobin, and elevated unconjugated bilirubin. These should be performed before more specific testing (eg, hemoglobin electrophoresis, glucose-6-phosphate dehydrogenase, osmotic fragility).

Closing the encounter
In the wrap-up discussion, the first step is to discuss the likely diagnosis along with an assessment of the diagnostic uncertainty. If a patient has pathognomonic findings for a particular disease, you should explain the significance of them. If you are uncertain about the diagnosis, say so clearly, but reassure the patient that you will work with them to identify the cause.
Regarding diagnostic tests, if invasive studies are necessary (eg, cystoscopy in an elderly smoker with hematuria), explain the rationale for the tests. Allow time for questions, and assess the patient's readiness to undergo the studies you recommend.
Diagnostic studies
Patients with an abnormal urine color should have a urinalysis with microscopic analysis of urinary sediment (ie, for casts, crystals, etc.). Note that patients with myoglobinuria may have a positive test for hemoglobin on chemical ("dip stick") urinalysis without red blood cells on microscopic analysis. Other studies may include:
Electrolytes, blood urea nitrogen, creatinine
Liver function tests (eg, direct and indirect bilirubin)
Urine culture
Complete blood count (and peripheral smear, reticulocyte count)
Muscle enzymes (eg, creatinine kinase, aspartate aminotransferase [AST])
CT urogram (for identifying kidney stones)
Liver/biliary CT scan, ultrasound
Cystoscopy
Patients with hematuria should have evaluation of both the upper and lower urinary tract. Typical studies include CT urogram and cystoscopy, but the specific evaluation may be individualized.
If hemolytic anemia is suspected, start with a complete blood count, reticulocyte count, and peripheral smear. Supportive findings include elevated lactate dehydrogenase, low haptoglobin, and elevated unconjugated bilirubin. These should be performed before more specific testing (eg, hemoglobin electrophoresis, glucose-6-phosphate dehydrogenase, osmotic fragility).

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