The Lord smote him - "And after all these things the Word of the Lord smote his bowels," etc. - Targum.

After all this the Lord smote him in his bowels with an incurable disease. What it was is not agreed upon; some take it be an "hernia", or rupture; others, the falling of the "anus", or a fistula in it; others, the colic, or iliac passion; but generally it is thought to be a dysentery, or bloody flux; the Targum is,"the Word of the Lord broke him.''

The second punishment fell upon the body and life of the king. The Lord smote him in his bowels to (with) disease, for which there was no healing. מרפּא לאין is in apposition to לחלי, literally, "to not being healing."

And after all this the LORD smote him in his bowels with an incurable disease.

21:12-20 A warning from God was sent to Jehoram. The Spirit of prophecy might direct Elijah to prepare this writing in the foresight of Jehoram's crimes. He is plainly told that his sin should certainly ruin him. But no marvel that sinners are not frightened from sin, and to repentance, by the threatenings of misery in another world, when the certainty of misery in this world, the sinking of their estates, and the ruin of their health, will not restrain them from vicious courses. See Jehoram here stripped of all his comforts. Thus God plainly showed that the controversy was with him, and his house. He had slain all his brethren to strengthen himself; now, all his sons are slain but one. David's house must not be wholly destroyed, like those of Israel's kings, because a blessing was in it; that of the Messiah. Good men may be afflicted with diseases; but to them they are fatherly chastisements, and by the support of Divine consolations the soul may dwell at ease, even when the body lies in pain. To be sick and poor, sick and solitary, but especially to be sick and in sin, sick and under the curse of God, sick and without grace to bear it, is a most deplorable case. Wickedness and profaneness make men despicable, even in the eyes of those who have but little religion.