(CNN) -- The injuries don't appear life-threatening. They could be wounded legs and arms, caused by being pinned under falling debris from the earthquake.
But for some in Haiti, who are pulled out alive from the rubble, another medical emergency awaits them. Days later these crush injuries can cause kidney failure then death, experts say.
Kidney failure has been identified by the Centers for Disease Control and Prevention as one of the most urgent public health concerns in Haiti following the 7.0-magnitude earthquake.
"If head injuries are the hallmark of the war in Afghanistan, the Haiti earthquake will be known for crush injuries," said Dr. Sanjay Gupta, CNN's chief medical correspondent reporting from Haiti's capital, Port-au-Prince.
The condition, known as rhabdomyolysis, occurs when muscles have been crushed. The muscle ruptures, releasing its cellular content, including particles called myoglobin, into the body. These particles get caught in the kidneys.
"This myoglobin comes into the kidney and it jellifies into the tubular system that drains the urine from the kidney and it blocks the kidney," said Dr. Raymond Vanholder, a Belgian nephrologist. "As a consequence, people stop producing urine and everything that goes out in the urine comes into the body and intoxicates them."
If not hydrated regularly, the person is unable to flush out the myoglobin.
"Its one of the concerns of people who are injured, especially in something as terrible as what's going on in Haiti right now," said Dr. Janis Orlowski, senior vice president of medical affairs and chief medical officer at the Washington Hospital Center. "And it's one of the causes for people dying a day or two after they have sustained a crush or traumatic injury."
Four to 33 percent of patients with rhabdomyolysis will develop kidney failure, according to research.
Rhabdomyolysis was described by doctors who found that the survivors of the World War II bombings in London were dying days later -- although their injuries had been nonlife-threatening. The victims developed dark urine and subsequently died of kidney failure.
People usually develop rhabdomyolysis after crush injuries, produced by events such as earthquakes, mine collapses, traffic accidents and severe beatings. Patients have vague symptoms like swollen extremities and muscle weakness, but one glaring indicator of kidney trouble is the dark, cola-colored urine.
The condition is treatable with round-the-clock medical care, hydration and dialysis -- but much of these are lacking in Haiti. Dr. Pascal Goldschmidt, dean of the University of Miami Miller School of Medicine treated an 18-year-old Haitian crush-injury survivor who had to be airlifted to the U.S. because he had developed a significant complication -- acute renal failure -- triggered by rhabdomyolysis. The young man is in recovery.
Sometimes the limb must be amputated to save a person's life.
"The initial instinct for most people is to try to save the leg; it'd be too morbid not to," Gupta reported. "But we also know now that's not always the right answer." By trying to preserve the limb, doctors run the risk of infection, gangrene and rhabdomyolysis.
"Removing a limb could mean saving a life," he said.
Whether amputation should be considered depends "on how long they've been trapped, how much muscle has been trapped -- a lot of factors go into that," said Dr. Darren J. Malinoski, assistant professor of surgery at the University of California, Irvine School of Medicine. "It's possible removing severely crushed extremity, with low chance of functional recovery and causing toxicity, might prevent kidney failure and possibly death"
Malinoski, who researched rhabdomyolysis, said it's impossible to say what kind of circumstances doctors in Haiti face, but generally, amputations, should occur before the urine output decreases.
This is a particularly brutal procedure in Haiti right now as doctors often have to perform amputations without painkillers, Gupta said. "Without proper equipment, doctors are telling me they are using hacksaws to perform these operations, and using vodka to sterilize the hacksaws," he said. "There's hardly any anesthesia, or post-operative care or blood to transfuse someone."
Crushed limbs can also cause other medical complications. The release of other chemicals from the ruptured muscle -- including potassium and phosphate -- also can result in hyperkalemia -- too much potassium in the blood stream which causes heart problems -- and sudden cardiac death.
To address this particular emergency, the Renal Disaster Relief Task Force, an international team that specializes in renal care after major disasters, has been deployed to Haiti. The team works with Doctors Without Borders/Médecins Sans Frontières.
The Renal Disaster Relief Task Force formed after the 1988 earthquake in Armenia. The 6.9-magnitude earthquake killed between 26,000 and 50,000 people and left many of the survivors with what seemed like nonlife-threatening crush wounds in their extremities. But more than 600 of them developed kidney failure and there were not enough resources to treat all the cases.
Vanholder, who coordinates the task force, speaking from Ghent, Belgium, said its first team in Haiti arrived Friday but encountered severe challenges setting up its dialysis unit.
"Due to conditions, chaos and difficulties with our logistics and the airport which has been clogged, we have been waiting for material for many days for the dialysis unit," he said. The clinic became operational two days ago and the small team of nephrology nurses and one doctor are treating about 20 patients for kidney problems.
The task force expects two more nephrology teams to arrive in Haiti this week.
CNN's Dr. Sanjay Gupta, Saundra Young and Rebecca Leibowitz contributed to this report.