largely determined by the proportion of solids in solution, of which urea is the chief. The average composition of normal urine (which of course varies under differing diets and physio- logical conditions) is as follows: Water (average daily amount) 1500 c.c. Urea (approximately) 30 grams. Uric acid 1 gram. Creatin 1.5 grams. Sulphuric acid 4 grams. Phosphoric acid 3 grams. Inorganic salts 10 grams. Pigments Variable. The specific gravity of the urine is, of course, in- creased by any influence which (a) increases the FUNCTIONAL DIAGNOSIS 123 amount of solids, or (b) decreases the quantity of water in the secretion. Glycosuria (sugar in the urine) is by far the most important of the first class of pathological condi- tions. In diabetes milletus the percentage of sugar ranges from 0.5 to 8 per cent, and the specific grav- ity varies between 1.035 and 1.040. In fevers the increase of urea raises the density. Acute and chronic parenchymatous nephritis are conspicuous examples of the latter variety. In these diseases the glomeruli are congested and degener- ated, hence the amount of water secreted is lessened and the density of the urine correspondingly in- creased. Specific gravity is decreased, on the other hand, by any condition which (a) reduces the amount of solids, or (b) increases the quantity of water se- creted. Interstitial nephritis (atrophied or contracted kid- ney) and amyloid kidney are instances of the former variety. Diabetes insipidus furnishes a typical example of the latter class. In this disease the quantity of wa- tery secretion is largely increased, but not the se- cretion of organic solids. Hyperacidity is found in gout, lithiosis, and acute rheumatism, owing to the preponderance of uric acid; in fevers owing to the abundance of urea; and in diabetes because of the presence of acetons. Alkalinity occurs in cystitis, prostatitis, malignant 124 FUNCTIONAL DIAGNOSIS diseases of urinary tract, paralyses, and any other condition which causes long retention and conse- quent fermentation of the urine. Profuse hematuria renders the urine alkaline.
<Callout type="important" title="Urea's Significance">Urea is the most important ingredient of normal urine, as it is also the most important of the nitrogenous excreta, which are practically all excreted in the urine. Urea is by far the largest of the end products of proteid digestion.</Callout>
Increase of urea in the urine is the direct outcome of increased metabolism. Hence it is found in fevers and inflammatory diseases, in diabetes, malaria, and pernicious anemia.
Decrease of urea on the other hand points to abnormal decrease of metabolism, and is seen in chronic nephritis, gout, rheumatism, malignant and constitutional diseases, not so much as a result of these diseases, but as an accompaniment, due to the same metabolic disturbance as is causing the dis- ease.
Uremia is sooner or later the upshot of a suppres- sion of urea in the urine. Formerly it was thought to be due to the accumulation of urea in the blood (hence the name), but latterly it is agreed that the process of metabolism of which urea is normally the end-product is diverted, and produces abnormal toxins which are not eliminated by the kidneys, but circulate in the blood and poison the nerve centres.
Ureteral Function. — The urine which is being con- stantly formed in the kidney passes into the ureter, down which it is carried by the combined forces of gravity and peristalsis to the bladder, into which it is forced intermittently. The peristaltic contrac- tions occur automatically every ten to twenty sec- onds, beginning at the pelvic opening and passing downward in the form of a wave. The ureter is- therefore normally always filled with urine, each wave forcing out about 1-2 c.c. into the bladder.
<Callout type="warning" title="Ureteral Obstruction">The ureter is not infrequently the seat of obstruction due to impacted calculus, shreds of malignant growth, stricture, spasm, or external 126 FUNCTIONAL DIAGNOSIS pressure from pelvic and abdominal tumors. The obstruction, of course, prevents the normal on-flow of urine and produces stasis in the renal pelvis (hydronephrosis), and if bilateral, eventual suppres- sion of urine.</Callout>
Infection to and from the bladder and kidney is occasionally carried by the ureters, causing pyelitis or cystitis as the case may be. Owing to the normal downward peristalsis, ascending infection is for- tunately rare, and descending infection has, of course, not so prolific a starting place.
The bladder serves as a reservoir for the urine until it is voided from the body by the act of urina- tion, being retained by the tonic contraction of the sphincter vescicae. It must be understood that the bladder, like the stomach, is always distended pre- cisely in proportion to the amount of its contents, its muscular coat being in a constant state of tonic contraction around these contents, so that the bladder is really always "full." What is usually spoken of as a full bladder is really a fully dis- tended bladder.
<Callout type="tip" title="Bladder Function">The distension of the bladder by urine stimulates a reflex contraction of the muscular coat, and relaxation of the sphincter vescicle, which would immediately empty the blad- der were it not opposed by a voluntary contraction of the sphincter.</Callout>
As soon as the brain relinquishes this voluntary opposition the sphincter relaxes and the urine is voided by the vescical contraction, aided toward the end of the act by abdominal muscles. The inhibitory con- trol of the brain can only be maintained up to a certain point of stimulation, be- yond which the spinal centre will act in spite of it.
The mechanism of defecation is similar to that of micturition. The feces are kept in the rectum by the contraction of the internal and external sphinc- ters. When the rectum becomes sufficiently dis- tended the distension stimulates a reflex contraction of the rectal muscles and relaxation of the internal sphincter by which the feces would be expelled but for the voluntary opposition of the external sphincter.
<Callout type="important" title="Defecation Mechanism">When this opposition is inhibited by the brain, the external sphincter relaxes, and defecation takes place. In forced defecation (and it is usually more or less forced) the abdominal muscles assist in ex- pelling the feces.</Callout>
Abnormal desire for stool, both as to frequency and urgency, is seen in pathological conditions of the rectum and anus.
Feces. — As already stated, under digestion, very little absorption of anything but water takes place in the large intestine, and the alkaline reaction in this part of the tract favors bacterial putrefaction. By the time, therefore, the material reaches the rec- tum, under normal conditions, three consummations are reached; (a) the substance remaining contains only waste matter; (b), it has acquired a relatively solid consistency, and (c) it is in an advanced state of decomposition.
<Callout type="risk" title="Feces Composition">The characteristic color of the feces is due to the bile-pigments ; their odor to the skatol. Lienteria, i.e., an abnormal quantity of undigested food in the feces, indicates, of course, that the alimentary tract is not properly disposing of the food.</Callout>
The temperature of the feces, owing to fermenta- tion, is higher than the body temperature — hence in taking rectal temperature care should be exercised not to insert the thermometer in a mass of feces.
Key Takeaways
- Urea is crucial for diagnosing metabolic conditions like diabetes and uremia.
- Urinary obstruction can lead to severe kidney damage if not treated promptly.
- Bladder control involves both voluntary and involuntary mechanisms.
Practical Tips
- Monitor urine color and consistency as indicators of hydration and overall health.
- Recognize the importance of regular urinalysis in diagnosing metabolic disorders.
- Be aware of signs of urinary obstruction, such as pain or reduced urine output.
Warnings & Risks
- Uremia can be life-threatening if not managed properly.
- Infections can spread from the bladder to the kidneys through the ureters.
- Bladder control issues may indicate underlying neurological conditions.
Modern Application
Understanding urine composition and function remains crucial for modern survival preparedness, especially in situations where medical facilities are limited. While many diagnostic tools have advanced, recognizing changes in urine can still provide valuable insights into health status. This knowledge helps in making informed decisions about hydration, nutrition, and overall well-being.
Frequently Asked Questions
Q: What does an increase in urea levels indicate?
An increase in urea levels typically indicates increased metabolism or conditions like diabetes, fevers, or inflammatory diseases.
Q: How can urinary obstruction be prevented?
Maintaining good hydration and avoiding the use of substances that may cause kidney stones can help prevent urinary obstruction.
Q: What are some signs of a bladder infection?
Signs include frequent urination, pain or burning during urination, cloudy urine, and fever. These symptoms should prompt immediate medical attention.