In pregnancy the kidneys always give evidence of a constant congestion, and the chief symptom of this is the great quantity of renal epithelium shed with the urine. This engorgement has given rise to the term "kidney of pregnancy." There has been much discussion of this condition, especially as to the possibility of differentiating it from beginning nephritis. In 227 consecutive cases of pregnancy in which the urine was examined at short intervals by myself throughout the entire gestation, there was always an enormous quantity of epithelium, and this presence of epithelium is so constant that its absence is a proof that pregnancy does not exist. It is as physiological as any other somatic change in the puerperium. Von Leyden and other German observers look upon the degenerative alteration in the epithelium of the renal tubules as pathological, but apparently more definite symptoms are necessary to make a diagnosis of significant nephritis.

Williams[118] says that in the examination of 1000 pregnant women at Johns Hopkins Hospital in Baltimore traces of albumin were found in 50 per cent. without subsequent serious disturbance, but where considerable albumin with casts other than hyaline was seen there were symptoms of toxemia later, and several of these went on into eclampsia. Fisher[119] held that red blood-corpuscles in these cases indicate acute nephritis; and granular and epithelial casts, chronic nephritis. Like the Johns Hopkins cases, he found albumin in 50 per cent. of his patients. Albumin in slight quantities is found to be extremely common toward the end of pregnancy. Meyer,[120] in an extensive study of the kidney in pregnancy, made at Copenhagen, found albumin in 5.4 per cent. of the women. During the last month of gestation 71 per cent. of the women showed albumin. Premature births occurred in 8 per cent. of the patients who had had albuminuria, but in 21.5 per cent. of the women who had had casts. Delicate tests for albumin are used by men who find these high averages, as a few leucocytes from leucorrhoea will give the reaction. Most of these cases have no clinical significance.

It is usually impossible to differentiate in pregnancy a lighting up of an old nephritis from a toxemia. Where there is a history of nephritis before the pregnancy, this often clears up the diagnosis. Nephritis is likely to manifest itself in pregnancy earlier than toxemia; albuminuric retinitis is commoner in nephritis, but these facts are no real help in differentiation.

The position of the uterus may be a cause of nephritis, according to the American Text-Book of Obstetrics; but De Lee and others hold that the growing womb cannot possibly be a cause. Many other origins have been suggested, but without sufficient proof.

The treatment of the nephritides of pregnancy is that described in chap. xiii for eclamptic symptoms. When albuminuric retinitis occurs, the medical tendency is to empty the uterus. All text-books counsel this procedure, but they give no convincing reasons for the advice. If the child is viable the therapeutic abortion might be done when necessary; if the child is not viable the operation is, of course, not licit. In the nephritis of pregnancy it is not certain that emptying the uterus artificially, with the entailed shock, is the best method of treatment; but, as a rule, nephritis is made worse by pregnancy, and the irritation lessens with the termination of gestation in some cases, but not in true chronic nephritis. Eclampsia is more toxic than nephritis, and the treatment may differ in important details: it certainly is doubtful that artificial abortion in eclampsia is the method of choice at present. I saw a case of albuminuric retinitis ten years ago, which could not have been worse. The woman was in the seventh month of gestation; she was nearly blind and half comatose. The albumin in her urine always was so great that it would not fully precipitate in a centrifuge tube, and every field under the microscope was covered with large casts in such enormous quantities that they were felted together. Yet the woman was carried on to term by Dr. Joseph O'Malley and delivered of a fully developed child. She since has had two other children at term who are perfectly healthy, and she herself could pass a life insurance examination. This is, of course, only one case, and it is exceptional; but it is impossible to say what will happen in any particular case—whether it will go on to death or recovery.

Both subacute and chronic parenchymatous nephritis show clinically much albumin, many casts, marked edema (except in very emaciated cases), absence of high blood-pressure, and the heart is not enlarged. This condition is caused commonly by chronic tuberculosis, syphilis, sepsis, and malignant tumors. With these clinical symptoms and the history, we may differentiate the nephritis of pregnancy from Bright's disease. Again, acute intestinal nephritis or glomerulonephritis has urinary findings like the nephritides just described, and there may be edema. The heart and the blood-vessels are normal. The cause is usually a pus microÖrganism, and there may be anemia from the sepsis. In subacute glomerulonephritis, or intestinal nephritis, the urinary findings are marked (much albumin and many casts), anemia is rather constant, the blood-pressure gradually goes up to 180 or 200, edema may be marked or absent. The cause is usually a pus microÖrganism. Chronic glomerulonephritis shows much epithelium and many casts (sometimes in showers), the blood-pressure is high, the heart is usually somewhat enlarged, there is polyuria and some blood, edema is common (but there are dry cases), albuminuric retinitis is rare, and anemia is marked and secondary. It may be difficult to find the cause of this chronic glomerulonephritis, but there is, as a rule, a history of tonsillitis, septic rheumatism, endocarditis, a true influenza, or the like infection. Primary arteriosclerotic contracted kidney shows hypertension and secondary circulatory disturbance. The urinary findings are comparatively slight and transient, and there is little or no anemia. The development is insidious, and the etiology is not known.

There is evidence of late to find a septic cause for most of the nephritides, such as infectious fevers, pyorrhea of the teeth, and like bacterial intoxications; in pregnancy the nephritis may be toxemic from sources that are not bacterial. It is extremely difficult, and not seldom impossible, to make any differentiation, as has been said. When the child is viable, whether the uterus should be emptied or not must be decided for the individual case; no general rule can be set down to cover all conditions.

One of the kidneys may be dislocated during pregnancy—usually the right kidney. If a floating kidney becomes twisted on its pedicle, abortion may be a consequence. The torsion may compress the renal blood-vessels and bring on acute hydronephrosis with high fever, great abdominal tenderness, and a peritonic facial expression.

Pyelitis of the renal pelvis is not seldom met in pregnancy. The gonococcus, colon bacillus, or some other pyogenic bacterium gets a nidus after pressure and lowered power of resistance. This condition is sometimes mistaken for appendicitis.

Catalepsy is a rare complication of pregnancy, in which the woman lies in an unconscious condition. The disease is a neurosis, but it might be mistaken for a toxic or uremic condition by a superficial observer. The infants of such women may be cataleptic, and may die as a consequence of the condition.