Professor and Associate Chair, University of Florida, College of Veterinary Medicine
Gainesville, FL, USA
The key to making a correct diagnosis depends on obtaining an accurate patient history and doing a complete physical examination. Obtaining a history is as much an art form as it is a scientific inquiry. It must be done as objectively as possible in order to obtain a truly accurate description of the patient's problems. The findings from the physical examination begins with the cognitive skills of the observer and then the correct interpretation of these findings. The mental images that are preserved from such clinical experiences are oftentimes the key for making future diagnoses of the same type of disorder. Therefore, it is no wonder that we can often say that "a picture is worth a thousand words". Because this seminar is strictly an image presentation, the written version will emphasize the clinical signs of several common clinical disorders.
Petechia are foci of pinpoint hemorrhages that can involve any of the soft tissues of the body. They usually signal the presence of a platelet disorder although they can also occur with vasculitis. Platelet disorders can arise from inadequate numbers (quantitative) or from impaired function (qualitative). Quantitative problems result from either peripheral destruction, impaired production or increased consumption. Platelet disorders commonly present clinically as small skin or mucous membrane pinpoint or ecchymotic hemorrhages or as melena associated with upper gastrointestinal bleeding. Rarely, the bleeding can be more dramatic as with frank hematuria. The most important diagnostic tests include the platelet count and the bleeding time. Think before doing a bleeding time test in a thrombocytopenic patient because the procedure can be complicated by uncontrolled hemorrhage
Coagulation factor deficiencies characterize as frank hemorrhaging into the body tissues; hematomas are of rather common occurrence. Ecchymoses and overt hemorrhagic diathesis require a rapid evaluation of the coagulation system with tests such as the prothrombin (PT) and partial thromboplastin times (PTT) and the activating clotting time (ACT). Factor deficiencies do not cause petechia unless a disorder involving platelets coexists (DIC). The history (including a drug history) should help to differentiate between congenital and acquired disorders.
In vivo hemolysis is the destruction of red blood cells within the vascular and extravascular spaces. Its causes are many ranging from toxins, infections, and drugs to autoimmunity. The classic picture of intravascular hemolysis includes: weakness, nausea, anemia, hemoglobinemia, icterus, and hemoglobin- and bilirubinuria. Note that "hemolyzers" hemolyze while "bleeders" bleed. Coagulogram profiles are generally normal with hemolytic disease unless a co-existing disorder such as DIC is present.
Hemoglobinuria vs. Hematuria vs Myoglobinuria vs Bilirubinuria
Hemoglobinuria is a product of hemolytic disease characterized as a dark port-wine-like colored urine that contains few intact RBC's. Hematuria is a typical red color and reflects bleeding anywhere along the urinary tract. Patients with a bleeding tendency can also bleed into their normal urinary tract. It is possible for some upper urinary tract lesions, such as a bleeding renal tumor, to have both hemoglobinuria (as a result of the blood becoming hemolyzed in the urinary bladder during storage) and hematuria. It is also possible for a fresh renal bleed to form clots in the urinary bladder and cause urinary outflow obstruction.
Myoglobinuria accompanies rhabdomyolysis. It will cause reddish brown pigmenturia and a positive test for blood on dipstick, but the sediment is devoid of RBC's.
Vomiting vs. Regurgitation vs. Retching
Vomiting is the actual forceful oral expulsion of gastrointestinal contents accompanying many different digestive tract disorders as well as those involving other organ systems as well. Regurgitation is the more passive bringing up of esophageal contents that most commonly accompanies esophageal disorders. Retching is a forceful but unproductive attempt to vomit that can occur with constrictive esophageal pathology. It can also occur following a coughing episode.
Localizing Significance of the Various Types of Vomitus
Clear mucoid-esophageal, gastric. Red blood--esophagus, stomach. Dark red ("coffee grounds")--gastric, pylorus, very proximal duodenum. Bile stained--small bowel; bile in vomitus attests to pyloric patency. Brown, malodorous (feculent)--distal small bowel, large bowel.
Blood in Stool
In general, bright red blood can originate anywhere distal to the mid-jejunum while dark brown-to-black stool (melena) comes from the stomach and proximal small bowel. However, a major bleed in the proximal bowel and its subsequent rapid passage can show as hematochezia. Oral or nasal bleeding can cause melena from swallowed blood.
Stranguria vs. Obstipation
The most important situation where this differentiation becomes significant is that involving the cat or dog with urinary obstruction. Stranguria in male dogs and cats almost always signifies urinary outlet obstruction and is therefore always considered as a medical emergency. The male cat with urethral obstruction will make repeated trips to the litter box, sometimes accompanied by vocalization reflecting the animal's discomfort. Over a matter of hours the cat will become anorectic, begin to vomit, and become mentally depressed. The obstipated patient shows a better systemic tolerance for its GI dilemma. It should be pointed out that females can also experience urinary outflow obstruction and trying to decide on patency by way of telephone might compromise the patient's well being.
Polyuria vs. Incontinence
The polyuric patient typically produces and voluntarily passes copious volumes of dilute urine often accompanied by polydipsia. Urinary incontinence is an unconscious passage of urine that occurs while the patient is lying down or sleeping; these animals urinate normally.
Blindness vs. Dementia
At first glance these two conditions might resemble each other to the uncritical observer. The blind patient will certainly bump into objects, especially in unfamiliar surroundings, and it will fail to respond to a menace gesture, but its other neurological functions are normal. The demented patient might not menace mainly because the brain is malfunctioning and consequently cannot register the threatening gesture while its visual pathways might very well be normal. This patient will have accompanying neurological abnormalities.
Neurologic vs. Metabolic Weakness
The signs accompanying neurological weakness will depend on the nature of the primary disorder. Most are usually continuous, sometimes progressive. They are commonly segmental or lateralizing in their distribution when caused by a focal lesion. Other neurological signs such as pain might be present if there is meningeal or dorsal nerve root pathology.
Metabolic weakness can also be continuous and progressive, but it can also be episodic as well. Patients with metabolic weakness tend not to segmentalize or lateralize their neurological abnormalities. The oculocephalic and pupillary light reflexes are usually retained with metabolic encephalopathy.
Lameness vs. Weakness
Lameness is the favoring of a limb because of discomfort. Depending on the distribution of the lesion, one or more limbs may be involved. In general the more distal the lesion, the less weight bearing that occurs. Pain and gross morphologic abnormalities can usually be detected. Weakness can be accompanied by pain, but it more commonly presents in the absence of pain and any favoring of a particular limb. Weakness can be regional or diffuse in its distribution.
Pain is any localized discomfort associated with a bodily disorder. It can originate from any organ system and be a source of major incapacitation to the patient. Animals will manifest its presence with either outward signs of discomfort (vocalization, biting, various motor movements), or they will show opposite signs characterized by a withdrawn behavior along with anorexia and mental depression (as commonly seen in cats). Identifying the source can sometimes be a challenge to the most experienced diagnostician.
Seizure vs. Syncope
Seizures are usually complex motor movements associated with abnormal cerebral function; alterations in the state of consciousness to varying degrees are commonly present. Typically, seizures have preictal, ictal and postictal components. Syncope is a loss of consciousness that lacks the three components of a seizure. Although most syncopal disorders are due to cardiac dysfunction it is possible where a cardiac cause of syncope can be accompanied by enough hypoxia to establish a seizure focus in the same patient. It is most commonly caused by abnormal cardiac excitation or conduction although it can more rarely occur with certain metabolic disorders as well. It is important (but not always easy) to be able to differentiate narcolepsy and cataplexy from seizures and syncope.
PRIMUM NON NOCERE